How Do Nitrates Affect Coral Coloration

Today we are talking brown corals and here each week we answer your questions related to reefing. This week we are answering aquaticnut86’s question “How and or why do higher levels of nitrate turn your corals brown?“

Today we are going to answer that question as well as take a larger look at SPS coral coloration and give some direct advice on achieving the best coloration possible with methods which absolutely will produce results. Before I share anything today It’s important to remind us all what the community thinks we know about corals is based on discussion, a lot of anecdotal evidence and really more or less just our collective best guesses. The most commonly shared thought processes are often based on strongly plausible theories backed with common experiences but still pretty far from proven fact. if pretty much everyone shares the same experiences is likely fairly accurate or at least the information is producing repeatable results even if the cause isn’t completely understood.

So that said, related to aquaticnut86’s question it’s very commonly believed that one of the major contributors to SPS corals losing their brilliant coloration and browning out is is high nutrients in the reef tank. high nutrients most commonly referring to high nitrates and phosphates. The belief is the high nutrient levels encourages rapid growth of the symbiotic algae within the corals tissue known as Zooxanthellae.

The Zooxanthellae is brownish in color and in the more of it contained within the corals tissue the browner the coral will appear. In extreme cases the Zooxanthellae population will be so high that the coral completely browns out and overtakes all of the corals natural coloration pigments. I think it is pretty well established that tanks with an abundance of phosphate and nitrate will brown out. Corals and tanks with very low nutrients will tend to have more colorful corals. However this is one of those causes where this is very far from universally true.

There are certainly plenty of low nutrient tanks which have brown corals and lowering nutrients after the fact doesn’t bring the coloration back for many reefers. If you are one of these reefers I think it is worthwhile to take a more holistic approach to coloration. While it certainly seems to be true that high nutrients cause SPS corals to brown out I think there are a couple things we should keep in mind. First low nutrient tanks are very frequently the result of good maintenance practices and the phrase “high nitrate and phosphate tank” can fairly frequently be exchanged with “poorly maintained tank”. High nitrates and phosphates are a direct result of an imbalance between nutrient input and export which in a vast majority of causes is going to result in a variety of chemistry related issues beyond just high nitrate and phosphate .

If we are honest with ourselves in many causes this is also indicative of the amount of general effort put into the tank. A while back someone commented on one of our videos one of the most insight comments I have heard all my years of reefing. “successful reefers are not good at maintaining aquariums, they are good at maintaining water and a successful reef tank filled with healthy, growing and colorful corals is just a result of being good at maintaining water. That is absolutely the case. The other element related to brown corals is high nutrients are very far from the only cause. I think we have all seen corals brown from handling or fragging, coral dips, significant lighting or chemistry changes, flow changes or even just from moving them from one area of the tank to another. Virtually any significant environmental change can cause the coral to almost completely brown out.

It’s hard to know what mechanism is at play here, does any stressful environmental change cause the coral react by promoting rapid growth or population expansion of the brown zooxanthellae? Do these factors somehow impact the corals natural florescent and non-florescent pigmentations? It’s hard to know for sure but I think it’s been pretty universally demonstrated that browning has a very direct link to environmental stresses which are primarily related to water chemistry, lighting, flow and physical trauma. So to bring this the overall point home I think it is important to keep that in mind while high nutrients might be a direct cause in many instances it can also be indicative of other issues as well, so if solving nutrients alone doesn’t bring out the coloration you are looking for it might be time to take a more holistic approach that looks at all of the environmental stressors that could cause this. This is where our very direct advice on achieving awesome coloration comes in.

While there are always a lucky few that fall outside the norm there is one single thing that 95% of all the most awesomely colored tanks out there share and that’s “stability”. Life has shown the ability to adapt to a seemingly endless array of environments and still maintain healthy reliable biological functions. however many organisms are not capable of adapting to constantly changing environments, particularly those organisms who have had only had to adapt to subtle environmental changes in the last ten thousand years or more. I think most reefers and scientists will agree that SPS corals fit into that category, while they can adapt and survive to a fairly wide range of environments they do best in stable environments. So with that in mind I will share what that means to the  team in terms of SPS coloration.

The first being water chemistry. I think we all universally agree that stable low nutrients is fairly critical to maintaining the best coloration. What low nutrients means varies a bit from reefer to reefer but most interpretations of low are likely going to produce results as long as they are stable. If you allow the nitrate and phosphate to rise significantly and then use huge water changes every 3 months, chemicals or medias to reduce them rapidly it can certainly brown the corals out or simply keep them that way if they are already in that state. There are a hundred ways to maintain stable low nutrients starting with managing the amount of food you put in the tank. Reducing foods is obviously the easiest and most sustainable way.

Last update was in: April 17 2019, 4:28 pm

Carbon dosing methods like Zeovit , Red seas no3 -po4 x or vodka, Well designed Refigiums, Algae scrubbers, quality skimmers, frequently replaced filter socks or automated filter pad solutions like the roller mat, and of course just a regular water change schedule. Stable salinity as well as calcium, alkalinity, magnesium and potentially elements like strontium and potassium are all important. Salinity is probably the most important because as that raises and lowers every single element level is impacted as they become more and less concentrated. However right behind that is alkalinity.

Alkalinity is the one element I can tell you with complete confidence is the number one perimeter all of the best SPS tanks monitor closely. Stable alkalinity has has proven to have all types of positive impacts on on both coloration and growth. A lot of the pros test it daily without fail. Right behind that I believe is acidity of the water and maintaining a stable pH. There are fairly well documented calcification and growth benefits and likely overall health benefits assumed with higher pHs near 8. 3. While I won’t go as far as to say there are guaranteed coloration benefits with a stable pH I do think it’s very likely especially when done in unison with other elements of stability. Since the most significant cause of large PH swings are related to carbon dioxide in the tank the best solutions address that. The most popular being lighting a refugium at night to uptake excess co2. dosing kalkwasseror high Ph 2 part at night , feeding your skimmer with fresh air from outside your home and using a co2 scrubber media on the intake of your skimmer is also becoming pretty popular.

Stability in lighting is also essential. not only implementing the right spectrum and intensity but also resisting the temptation to mess with it constantly. historically this was easy because you can’t make a lot of adjustments to Halides and T5 lighting. More or less use bulbs everyone else had success with, plug them in and the corals grow and color brilliantly . With LEDs that can be a lot harder. Make sure to do some research and select spectrum and intensity settings other people are having success with rather than what looks good to the eye. What looks good to the eye has zero correlation to what’s healthy to the coral. Behind that set it and forget it.

If you make significant changes I would make them in incremental stages slowly over 4-8weeks and then leave them that way for 3-6 months to measure results. One of the causes of corals browning out related to lighting is often thought to not be enough light and the corals increase their zooxanthelle population to produce more nutrients and compensate. In this case many reefer will find ways to increase the intensity of the light. just keep in mind that too much light is not horse power where more is always better and light is 100 times as likely to kill the coral than not enough. One other element to consider related to this is the zooxanthelle are using elements like light, water, co2, nitrate and phosphate to produce amino acids and carbohydrates for the coral. Rather than using light to increase the nutrients the zooxanthelle produce.

Many of reefers supplement light by dosing amino acids, carbohydrates and  foods like reef chili or PE calanusor hakari’s cyclopods. Providing these elements of nutrition reduces the reliance on the zooxanthellae population and in turn is believed to provide better coloration. However like the other things we mentioned today to be beneficial they need to be dosed regularly and provide a stable source of nutrients or you might actually have the opposite results as the corals continually try and compensate for the irregular availability of nutrients. For instance on the BRS160 we maintain near zero nitrate and phosphate with the zeovit system. Some people refer to this system as a ultra low nutrient system but I think that pretty far from the case. While it might be ultra low nitrate and phosphate the BRS160 is what I would refer to as a very high nutrient system because we feed fairly heavily, dose a variety of amino’s, particulate foods and the water column is what I’d refer to as nutrient rich . because of that the corals have less reliance on the zooxanthellae and in turn limited demand for nitrate orphosphate as well.

Flow is also an environmental issue however enough flow is pretty easy to achieve with today’s power head and most reefers don’t change them often so this is typically a pretty stable component of most reef tanks. I would try and get that 30-50 times turn over with varied flow patterns most of SPS tanks do best in. Most of these elements are all likely to have the biggest impact in reference to the browning impacts related to zooxanthellae populations however behind that is the corals natural Florissant and non Florissant color pigments. The two most common way to promote the creation of these pigments and better coloration of the actual coral itself is lighting and spectrum changes but right behind that is trace elements. At this point trace elements have a fairly well accepted impact on coloration.

There are hundreds of trace element products out there and I guess I don’t recommend randomly dosing them and hoping for results. The best options have very specific dosing recommendations and results tied to them. The most common being the coloration enhancers by Korallen-Zucht and red seas program. Both of these are straight forward and have distinct results from following their program. Hope we clarified some questions you may have had on SPS browning and coloration today.