We will start by talking about why do you have algae in your tank, is it a problem? A fresh look at limiting factors, predators, poisons and inhospitable environments for algae. Our focus is going to be on algae but most of what we talk about today also applies to other photosynthetic pest organisms like cyano, diatoms and dinoflagellates as well.
So the moment we see algae growing in our tanks the perception is something is wrong and we are maintaining our tanks poorly, overfeeding or some piece of equipment is undersized. A more accurate view is that’s only the case if the algae prevents you from enjoying the tank somehow or it is harming other organisms in the tank. Fact is algae is a very natural occurrence in every ocean reef in the world, desirable when in balance with other elements of the reef and without it all kinds of herbivorous fish likely wouldn’t exist as we know them today. So all that said admittedly in the reef tank algae is more often than not a sign of poor feeding, maintenance, husbandry or other issues. Algae in the reef tank is often just ugly, kills corals, increases maintenance requirements and overall undesirable but I think part of understanding how to keep it in check is understanding that it is a completely normal occurrence even in very healthy environment.
Before we get too far into this I want to point out there is a huge difference between maintaining a tank that focuses on preventing outbreaks and dealing with one after the fact. This is an instance where an ounce of prevention is worth a pound of cure and it literally is 16 times if not 160 times as hard to get the algae back into balance with your tank after an outbreak as it is to prevent the outbreak in the first place. I don’t think any of us need to see another video on feeding less and doing more water changes which is fairly obvious good advice. What we are going to talk about today is the presumption that you ran into an issue and experiencing an outbreak, most of this information you can apply in some way to preventing itin the first place but dealing with it after the fact does mean you need to take some of these elements to more extreme levels than you would just preventing it. Most of the advice out there is naturally based off personal anecdotal experiences which often seem compelling but not always right and all too often the advice is singularly focused reducing phosphate and nitrate.
While frequently effective Phosphate and nitrate are just a couple of pieces of all this. Reducing them or getting them into balance with the tank can be the complete solution but in other causes has almost no impact and in these cases we need to think beyond just this one simple element. It is helpful to remember that typical ocean levels for phosphate and nitrate are hundreds of times lower than what is found in our tanks and algae still thrives in the oceans reefs. This isn’t a completely fair comparison because there is an infinite supply at these ultra-low levels in the ocean but understanding that algae can survive or even thrive in ultra-low nutrient environments is important to attacking the problem. When we encounter an algae issue that doesn’t responded to standard good feeding and maintenance habits it is time to take a more global approach to algae which focuses on what algae needs to rapidly reproduce itself so we can control all of those elements better, primarily light, water, carbon dioxide, and various inorganic nutrients like nitrogen, phosphate, or to some degree, calcium, magnesium, sodium, iron, silica, copper, zinc and other nutrients.
Any one of these things could potentially be a limiting factor for algae growth with some species meaning either abundance of one or critically low levels or both can be the cause or cure for your algae growth. Rather than start with inorganic nutrients I am going to start with the number one limiting factor to algae growth, light. Without a source of light none of these photosynthetic pests will grow. So what if you refuse to reduce your light output? Well you can absolutely consider maintaining the same PAR intensity levels but shifting the spectrum. While not proven and certainly not applicable to every species of photosynthetic pest organism it has been theorized by countless hobbyists for decades that the red and yellow spectrums encourage algae growth so it only makes sense to reduce these spectrums when you really challenged battling it out with a difficult to deal with algae. When dealing with an already existing outbreak where other solutions are not working you might want to consider almost completely removing the red and yellow spectrum for a prolonged period of time and see how the algae or photosynthetic pest organism responds. Now it’s not likely you will want to run the tank that way permanently just because it is visually too blue for most people’s liking but it could be part of that 16 ounces of cure and worth exploring when other things are not working. Keep in mind that every situation is different and don’t expect miracles just by tuning spectrum in every case but it’s worth exploring as an overall strategy. This does leads us into the next limiting factor to algae growth inorganic nutrients.
I don’t want to down play the role of nitrate and phosphate in feeding algae or other photosynthetic pest organisms growth because controlling these elements can be very effective methods of preventing, controlling and reducing them. Reefers just shouldn’t get discouraged if it doesn’t work or feel like they are the worst reefer out there if despite all their efforts they can’t solve their algae issue with nutrient reduction alone. A lot of the advice out there can send you chasing your tail in relation to nutrients. It’s pretty common for the question and advice chain to go something like this. I have all kinds of algae how do I get rid of it? Answer: get your nutrients in control with one camp telling you to use filter medias like GFO to get them down, another camp telling you that’s just a band aid for the real issue and you need to either stop adding nutrients or up your nutrient export game. Both are right and effective in their own ways. In either case you follow that advice and get the nutrients down and test near undetectable nitrate and phosphate but the algae is still there.
Most common response to that: well the algae is up taking the nutrients faster than you can test for them which is a real issue in many cases but honestly if that’s the answer and test results of zero still represents a mystery problem then why did you tell me to test in the first place? So the answer to that is commonly reduce basically every source of nutrients to almost zero with RO/DI water, the stingiest feeding schedule known to man, 50% weekly water changes and then physically remove all the algae. if you can reduce biomass of total algae in the tank to 10% or less of what was in there before by hand then the limited amount of algae that is left over shouldn’t be able to uptake it faster than you can test for it any longer and you can Identify if excess nutrient input or export really is the issue. yet algae is still growing and the next set of advice is your rock has found some mysterious way of binding inorganic phosphate and nitrate and now leaching it out back into the tank,and even though you have undetectable levels of nutrients and physically ripped out most of the algae this is because this tiny amount of left over algae is still sucking up the nutrients faster than you can test for them and the only answer is to break down the tank and give the rock an acid bath.
This is where I put the brakes on this never ending chain of chasing nutrients. fact is some algaes survive and even thrive in low nutrient environments and this strategy just isn’t working so it is time to look elsewhere or at least take a different approach to nutrient control. So hearing that diatribe it might seem like I don’t think nutrients are a big deal and that’s not the case, high nutrients are more commonly than not the issue and controlling them are very often the solution but if that doesn’t work we need to get off that train eventually. So this is how we suggest you approach phosphate and nitrogen in relation to algae.
Number one thing I’d like to get across is don’t be lazy, remove as much as you can by hand. This is probably you best nutrient export method in the tank. Not only does the algae up take the nutrients and by removing the algae from the tank, you effectively remove the nutrients from the tank regardless of the nutrient source the opposite is true as well. If your goal is to let the algae disappear on its own rather than remove it remember than what you are really saying is I’m going to let it die, decay and break down into nitrogen and phosphate to feed new algae issues. Assuming the fish are going to eat it is short sighted as well because they are going to convert much of the nitrogen into ammonia and extreme it through their gills and release much of the phosphate they eat in their waste so letting algae die in the tank or get eaten is pretty short sighted, you really need to remove it to get the nitrogen and phosphate permanently out of the tank.
Next control the source of nutrients which is like 90% fish and coral foods. There are other sources like your source water and potentially rock but if we are talking nutrient input to the tank you are doing yourself a favor by focusing number one on fish food. There is no magic amount to feed your fish other than just enough that they look healthy which for many is once a day and a pretty small amount. These pellets may look small but remember these fish are tiny with tiny bellies they don’t need as much as they would like to make you believe. I think the best advice I can give is if you have a nutrient based algae issue immediately stop feeding dry pellet or flake foods and if you are using an automatic feeder stop using it. There are a few reasons I say this, first how much you feed is most often just a perception of what you personally think is enough. Pellets are super nutrient dense meaning a teaspoon of pellets is probably similar to 7 or 8 teaspoons of frozen food. I guess I’d consider them like a vitamin fortified weight gainer shake where a single glass has an entire daily calorie count for an average person. A little just goes a lot further than it would seem visually.
Frozen foods are often like 85% water so even though it seems like you are feeding a lot with a single cube you are most often adding a much smaller amount of total nitrogen and phosphate to the tank with each feeding and the amount is constant from day to day. So the fish are getting what they need and visually to you it often looks like it as well. The other reason is frozen foods don’t deteriorate in the tank as fast as pellets so more is eaten by the tanks inhabitants over the next few hours so a larger portion of the nitrogen and phosphate added to the tank will be essentially bound up in the fish’s biomass as tissue growth. They won’t utilize it all but very frequently more than less controlled feedings of pellets. Generally speaking I have just found way fewer issues with excess nutrients when reefers feed frozen foods. Particularly simple foods without a lot of additives like PE Mysis or Hikari Canadian Mysis which are mainstay of what I feed. That doesn’t mean that pellets and more complex foods don’t have their place but you absolutely need to be more vigilant about amount and frequency with these foods. Another two major nitrogen and phosphate input sources I’ll mention are your source water and rock. End of story.
I think any reefer who is in this for the long haul is going to benefit greatly from an RO/DI system for a whole variety of reasons. It’s just impossible to know what types of contaminants are in your water ranging from forms of nitrogen and phosphate that we are talking about today to metals, disinfection by products and a whole slew of unknowns. Basically starting with high quality source water is one of the only legit methods of maintaining high quality reef tank water. There is also a lot of talk about rock leaching nutrients into the tank. I guess I don’t buy into this as a major source the same way others do and I will share why. It is true that new wet or dry rock often has a lot of dead or decaying organic matter on the surface. The organic matter will release nitrogen and phosphate into the tank as it decays. This is why curing your new rock is an important step. We need to give the rock time to rid itself of that organic matter. If you are using dry rock you can just soak it in heated saltwater which will often cure and cycle the rock at the same time as the organics feed the beginnings of the nitrogen cycle. For quicker results where the organics break down rapidly some reefers will use things like bleach or acid?The part I don’t really buy into is the thought process that established multi year old rockbinding inorganic forms of nitrogen and phosphate directly to the rocks surface and it later releases or leaches it like some kind of nutrient battery. I guess I have never seen any science that can explain how these reactions would occur,most of the times I have seen claims that this is happen it is also coupled with the claim that the reason they test zero nutrients is because the algae is taking it up so fast you can test for it. It’s just a big leap to assume the rock is leaching nutrients you can’t even show exist in the tank, even after removing the algae.
I think the biggest reason I don’t think this is happening to a large degree is its almost all based on unconfirmed theory and in a vast majority of tanks out there the calcium carbonate based rock does not seem to be doing this. I just can’t think of a reason why some tanks would have this type of reaction and not others. At least not one that we wouldn’t have easily identified and proven by now. So that said maybe I am wrong and this is happening but there is one more piece it. For it to be the source of your algae issues it has to be releasing a pretty considerable amount of nitrogen on a daily bases, enough that it is relevant to the amount of nitrogen and phosphate added from foods daily. If it’s a tiny fraction of the food base nutrients it very likely is not the cause of your issue. Just to be completely clear we are not talking about rock in a brand new system which is covered in decaying or diving organics which absolutely will add nutrients to your tank. We are discussing established cycled rock. If you do believe this is happening I think the best approach might be to attempt some tests to confirm it before chasing the resulting invasive solutions like acid baths.
Good one would be to just take a piece out and soak it in a bucket of heated saltwater with flow. If it’s the case that the rock is a major source of nutrients, enough that it is even relevant to the conversation in relation to the amount of nutrients coming from your food it is not only going to be detectable in the bucket but it should be detectable in something close to a single day and rise rapidly after. If it takes a week to be detectable that’s both to slow to be the real source of your issue and also, more likely some type of organic material on the rock decaying from the change of environment.
Ok so let’s assume you got the nutrient input under control. The next element is nutrient export. For all of these methods I guess I will start in order of what I would recommend. The first is probably just a healthy tank full of growing corals all of the corals will utilize nitrate and phosphate in the tank and generally in a natural healthy proportion. So filling the tank with growing corals might be the best nutrient reduction stratify you can have. Fast growing corals like softies, polyps and xenia are awesome nutrient reducers but I have seen SPS tanks with large colonies and similar effects. Equipment like protein skimmers, filter socks and newer items like the Rollermat all remove food before they have the chance to break down into inorganic nutrients like nitrate and phosphate. Maintaining these pieces of equipment is going to be one of the most effective things you do with a nutrient export strategy. I will say the roller mat is easy the number one coolest thing we have put on the tank. I won’t set up another tank without one. Not only is the tank visually crystal clear but it just removes a vast majority of uneaten foods and fish turds before they have a chance to break down. It’s not cheap but I personally believe it has the potential to be more effective than many skimmers in the same price range.
Next is a solid water change schedule, there are a hundred reasons to have a solid water change schedule. If you nutrients are sky high I think this is also the best way to reduce them as well. Three or four 30% water changes done fairly close to each other will be the easiest way put there to get the nutrients down initially and you don’t have to bother or worry about chemicals. I am going to throw chemicals and Medias in here next because they can be ridiculously effective. I personally don’t have any nitrate removal medias I would recommend as effective and safe solutions for a reef tank but there are some phosphate removal options like GFO which can work miracles not only preventing but also eradicating algae. The main reason for that is because it’s cheap and easy. Just adding a GFO reactor or even media bag to the system can bring the levels below 0. 0 3or even zero which I’d say in half the cases visually solves your algae issue very quickly. Without the phosphate it doesn’t matter how much light, nitrate, carbon or water there is the algae is unable to grow normally. Again it doesn’t work on every last type of algae but it does work on a lot of them. For me the only real downside to GFO is it often works so well and the result is such a sharp looking tank that it can mask other problems like elevated nitrate which eventually will be a problem in a variety of ways.
Often poor colored or unhealthy corals, unhealthy fish and with extreme levels of nitrate the moment you let the phosphate levels rise don’t be surprised when algae gets out of hand fast. I think it’s also important to remember that everything in the tank including corals require some amount of phosphate to grow so a level of zero has its own set of issues even if algae isn’t one of them. I do recommend GFO to most reefers particularly new ones because the benefits outweigh the detractors but there are some more balanced approaches to nutrients I think intermediate to advanced reefers should gravitate to.
Next nutrient export method is the whole array of carbon dosing methods which promote bacteria to remove the nitrate and phosphate for you. Either by being removed in the skimmer or processing the nitrate into nitrogen gas. Carbon dosing is things like vodka or vinegar dosing, bio pellets or the commercialized options like red seas nopo4x or KZ’s Zeovit program. Carbon dosing is really awesome on some elements because it often brings the nutrients down to almost nonexistent and you almost ensures you will never have an algae issue; however the downside is it is not necessarily a healthy environment for the corals to live this way and they often get pale or can even die when nutrients are consistently maintained that low. Typically this means in conjunction with carbon dosing you also dose products like amino acids, carbohydrates and other foods the corals can utilize for nutrients.
For the most part if you are a DIY minded person you can explore vodka and other methods like that. I guess I don’t recommend that to newer reefers or those who are not really in tune with their tank. It’s just a lot easier to use a product with real instructions and a large community who is following the same instructions as you which can share results, feedback and advice. Easiest one is probably red seas nopo 4x system combined with their reef energy system. On our setup we use Zeovit which is a bit cooler. People make it out to be a lot more complex than it really is. There is a reactor with a zeolite media which directly absorbs some of the ammonia directly and serves as a place for the bacteria to populate. Then you dose some bacteria food for the bacteria and some amino acids and or other foods like coral vitalizer. I think it takes me about 45 seconds a day. Result is near zero nitrate and phosphate levels. Zero signs of algae in the tank and the frags are showing some really awesome coloration.
All the guys tell me I sold out by going zero but in the same breath everyone admits the tank is coming along awesome and managing the Zeovit tank is a lot easier than it is commonly portrayed. Only real debate is can you get the same results with other methods. The answer is absolutely you can but I have to say so far this is the easiest and most constantly method of preventing algae and producing awesome coral coloration I have personally done. Refugium and algae scrubbers are another method of nitrogen and phosphate removal from the tank. More or less grow algae which consumes forms of nitrogen and phosphate, then grab a bunch out and throw it in the trash. You have effectively removed a pretty substantial amount of nitrogen and phosphate from the tank.
This is a good time to discuss why I have been using the word nitrogen rather than nitrate throughout this article. Even though reefers all complain about nitrate that’s just one type of nitrogen containing compounds in the tank. All plants, animals and corals for that matter require nitrogen to make amino acids, proteins and DNA. Most reefers talk almost exclusively about nitrate as the source of nitrogen for this and focus on only nitrate and phosphate as nutrients to reduce. However ammonia is also a nitrogen containing compound and many algae actually prefer ammonia over nitrate as their source of nitrogen. Meaning you can very possibly maintain a zero nitrate environment and still have tons of algae in the tank. Anyone who has dealt with Bryopsis how’s exactly how frustrating it can be to be to provide a near zero nitrate environment and still have algae thrive. If you are having issues fighting algae with now nitrate it is very possible the type of algae you are fighting is either capable if using ammonia as its nitrogen source or it may in fact even prefer ammonia. You may think you have no ammonia in your tank because it is cycled properly but that’s not the case, it is just very low levels of ammonia. The fish are constantly extracting excess nitrogen they received from their food through their kills in the form of ammonia and there are an enormous amount of organic matter decaying in the tank on a constant basis releasing ammonia into the water as well. There is a never ending 24/7 source of ammonia in the tank.
End of story if you have removed most of the algae by hand and run at or near zero nitrates for a prolonged period of time, removed most of the algae and still having issues it might be time to consider ammonia. I honestly don’t think anyone should use ammonia removal media because most of them deplete at unpredictable rates and cause a lot of issues with the tanks natural nitrogen cycle. I just have never seen many awesome reef tanks that use ammonia removal medias. With one exception the zeolite media that’s part of the Zeovit system directly removes some amount of ammonia directly. However in this case the medias, seems to be remove it at less aggressive rates, lasts months, seems to deplete gradually and there are thousands if not tens of thousands of tanks that have used this system effectively so I think this is a more than acceptable option of you want to use an ammonia removal media in a reef tank. For everyone else there is a more natural approach by operating a refugium which grows algae and completes with algae in the tank for nutrients. Most reefers consider this as an approach to removing nitrates from the tank but in a low nitrate situation it is likely also directly removing ammonia as well. Possible some of the algae we commonly grow in refugium might even prefer ammonia. Refugiums often get a bad rap because they don’t believe they are exporting enough nutrients. I guess I have seen the opposite and this is more of a question of proper expectations. Refugiums are just a component of an overall nutrient reduction strategy not designed to be the only component. You also need to understand what you put into it is what you will get out of it.
The tank has multi-hundred to multi-thousand dollar lights on it feeding the algae growing in the tank and light is absolutely the number one nutrient feeding your algae growth. If you have a $5 light from the hardware store lighting your refugium it isn’t fair to have the expectation that it is going to out-compete the algae in your tank for nutrients. I think a good option would be a low cost T5 fixture which is a good value from a coverage and intensity spectrum. On the setup we use the horticulture LED pendent from Kessil. Because we run Zeovit the algae grows pretty slow but what little does grow grows in here and not in the tank. One other element to the refugium concept is algae scrubbers. In this case it is theorized and commonly believed this type or refugium can completely remove the need for skimmers and other equipment.
The two differences here is the type of algae that grows in algae scrubber is a much less complex faster growing filamentous algae which can be harvested more frequently and theoretically removes a lot more nutrients from the tank. It’s also commonly believed that carbon dioxide is a limiting factor to algae growth in a standard refugium. In algae scrubbers the algae typically flows over a mat or screen of some type where the algae is exposed to virtually unlimited atmospheric carbon dioxide. Today’s algae scrubbers also tend to use high powered LED light sources with plant based growth spectrums. There was a patent preventing the commercialized production of scrubbers to hobbyists but that has expired and we are starting to see them pop up but for the most part it is still a DIY project. I bet within the year we start to see some legit contenders hit the market. Last bit of nutrient control I am going to mention is nitrate reactors. I think the most common being sulfur media reactors like this one from skimz.
Open and honest I have never used one personally but I know enough people who have and everyone says they work and they have never had an issue so I just don’t know why they are not more popular. At face value they do seem complex but probably less complex than a calcium reactor. Open and honest I think there are just easier ways to deal with nitrate in a reef system but I might strongly consider using one in a fish only system. Before we move on to predators and poisons there is one last potential limiting factor I wanted to explore, with carbon dioxide. Increasing carbon dioxide absolutely increases growth with many alleges, is almost a requirement in planted freshwater tanks and co2 is very commonly believed to be a limiting factor for algae in refugium so it only makes sense to consider it when you are having an outbreak in the display as well. . I don’t think reducing CO2 will eradicate algae from your system but in some cases it might just be the thing that reduces the growth down to a rate your fish, inverts and microfauna can keep it in control.
The best way to control CO2 in the tank is related to PH. At a PH of 7. 8 there is about three times as much CO2 in the water as at 8. 3 which I think is a pretty significant difference. Since there are all kinds of other benefits of maintaining a tank at 8. 3 including faster coral growth it’s certainly worth trying to achieve a PH of 8. 3 to also reduce the available CO2 by two thirds as part of a more complete solution when nothing else is working. Best ways to raise PH are maintaining your alkalinity properly, using kalkwasser for your calcium and alkalinity solution, using some co2 scrubber media on the intake of yours kimmer, using your skimmer to draw fresh air from outdoors or opening some windows in your home. Just opening your windows can make a huge impact on the CO2 levels of house and tank. Particularly if you have a lot of people or pets in the home and you have a pretty well sealed house. On a related note while it hasn’t been proven if it is related to CO2 or not it has been pretty well documented that dinoflagellates are often eradicated when the tank is maintained closer to 8. 3. That combined with a few day dark periods might be the complete solution.
No algae discussion is complete without discussing predators. I am not going to spend an enormous amount of time on them but it is these predators that most often keep the algae in check in the oceans reefs and they are going to hopefully to the same in your tank. I would even go as far to say that something as a simple as a single yellow tang can be the difference between success and failure for many reefers. Once you consider their behavior it isn’t all that surprising. More or less tangs like this spend their entire day pecking at the rock structure looking for algae to eat. As long as it is small they will eat almost anything. This is another one of those things that can give you a false sense of how your tank is doing because they are so good at keeping it clean in many cases you might not even notice your nutrient levels are raising over time until an outbreak happens. Tangs are an awesome preventative tool. We have two purple tangs in our aquarium for this reason. I will say fish like this often tend to work better as a preventative tool than after the fact simply because it’s of the volume they have to consume to eat their way through an existing issue rather than just consuming daily growth. Another good reason to remove as much by hand as possible when dealing with an issue. Snails and crabs are also popular. I have to say that I am 100% sold on trochus snails, even though they look very similar to your standard aster snail they seem to eat a much wider array of algae, a lot more of it and can flip themselves over better. I also find the larger nassarius snails to be decent at turning the sand over and I feel the most effective crabs in terms of consuming the widest array of algae are a handful of emerald crabs verses the dozens of hermits people normally use. Emeralds tend to be hardier as well. I would strongly recommend against buying those cleanup crew packages with hundreds of crabs and snails. Those are pretty rarely effective, mortality often feeds algae outbreaks more than it solves them and is really more about selling you stuff that it is about helping you and your tank.
To round all of this out we are going to talk when nothing else works. Poisons and inhospitable environments for algae and other photosynthetic pest organisms. There are some elements which have almost no risks like raising the PH which seems to knock back some pest organisms like dinoflagellates as well as high flow which almost always solves cyano but most of these are pretty much last resorts that I would say are generally safe but do have risks. I’m personally more willing to do these in tanks with a few hundred dollars with of corals rather than a few thousand because you never know what’s going to happen, you could lose some or all or just loose color in your SPS. I think the most effective of all these on algae is simple hydrogen peroxide. When applied directly to the algae it will almost always kill it. So if all else fails I think the best is to remove as much as possible by hand, drain the tank to expose the effective area and either spray 3% hydrogen peroxide right on it, drip it or the roots or use a syringe. Hydrogen peroxide is just oxygen and hydrogen so once it hits water it will ionize into those elements and pretty safe. Unless you use a ton there should be much of an impact on the tank other than temporarily raising the ORP. You of course don’t want to spray it directly on corals or it will likely kill them as well but in my experience it didn’t have much impact on coralline algae that may vary. I am going to go as far as to say for many of you hydrogen peroxide might just be the miracle you were waiting for. It’s fast and very effective. I will say there are some folks out there that dose it directly to their tank, you would never find me doing this to any tank with corals or fish I care about in and I will even go as far as not recommending it but some people swear by it and it might be worth some research if everything we talked about today didn’t work which to be frank I think is going to be rare as long as they were done correctly.
Another set worth mentioning are the red slime removers and chemicleans of the world. I honestly have no idea what’s in these at this point but I can tell you they work at virtually eliminating cyano when nothing else works and as long as you follow the instructions typically have no real impact on the tank. I have heard some rare instances of SPS browning out, and ultra-rare occurrences of corals dying but almost never an issue with LSP or softy tanks. Nothing is completely safe but I would say these types of products are generally safe. Related to that is KZ’s has a product that claims to go after Ciano’s food source. Hard to say what that means and I haven’t used it personally but seems like a more natural approach to cyano and seems to get good reviews. I will say cyano is one of those odd things that are actually capable of fixing atmospheric nitrogen gas in the right conditions so simply reducing nitrate might not be good enough. Would be really interesting to know what food source this product is targeting. Another one is dyno x or algae x from fauna marin which works particularly well on dinos and a handful of algae but this is one where I really would call it a last resort because it’s really unknown how this works and in fairly frequently has some pretty negative results in the tank.
Last one we will talk about today is raising magnesium levels to kill Bryopsis. No one knows why it seems to work. it was first found to work with Kent tech M and the original theory floated out there was it contained some kind of contaminant and it isn’t the magnesium itself but I have personally seen this work with so many forms of magnesium from mined in the US, evaporated dead sea salts and even pharmaceutical synthetic magnesium chloride that I just don’t think that’s likely. Much more likely that it is related to the magnesium or even chloride level. Even though reefers have been doing this for years there isn’t a standard method yet,probably because it only works in half the cases. Half the time it does absolutely nothing and in the other half it completely melts the Bryopsis before your eyes. For the most part it involves raising the magnesium level to around 1600 to 2000 parts per million and leaving it there for a month or so. Sometimes it starts to turn brown or white in days but sometimes it takes weeks. In a vast majority of cases the only thing affected is snails, crabs or other inverts which often die but corals and fish are rarely impacted.
Couple notes. You have an option here when you add this much salt you are going to raise the salinity substantially. You have a choice, you can run high salinity or you can dilute the tank to bring the salinity down. However be aware when you dilute the tank water to get the salinity back in line you are going to drop calcium, alkalinity and basically every other perimeter in the tank as well. You are going to want to adjust the calcium and alkalinity back up after but you can’t do much about the others. Either way when you are done the chemistry of your reef tank is going to be way out of line and the only solution is basically a plan that turns over as close to 100% of the water as possible. Your best bet is probably 4-5 30-40% water changes strung a few days apart after all the Bryopsis is gone. This will basically also ensure you are starting with nutrient free water as well. I have personally done this a dozen of times I can’t say this is the best way but I guess I would rather have my salinity too high than dozens if not more elements too low. So I raise the magnesium without diluting the salinity back down after. I also use BRS magnesium chloride rather than the Kent product because it works the same for me and way cheaper.
I have heard mixed reports from others but they basically fit the mixed results no matter what they use. As to if I would recommend the magnesium method to others. Bryopsis can be a tank killer so if nothing else works very often it is either this or rebooting the tank. If that’s the case for you I would try it. I would however read up on the forums for the exact method people are having the success raising and lowering the levels with currently which changes over time.