NUTRIENTS AND YOUR REEF TANK A DETAILED GUIDE
Nutrients are important to a successful reef ecosystem. Although for many years hobbyists were told to keep their nitrates and phosphates low or undetectable recent revelations have convinced most that in actuality low or undetectable nutrients can have disastrous effects such as the explosion of unwanted nuisance algae, cyanobacterium and dinoflagellates.
At Reef Chasers, we aim to keep both our Nitrates and Phosphates elevated and stable through natural feeding and overall system filtration. You can read more about Feeding and Filtration strategies here. Fish eat food and poop which serves to feed your corals in a very organic way. Organic food also deteriorates in the water column, producing ammonia that ultimately gets converted to Nitrate and Phosphate. This is why it's important for all aquariums to 'cycle' before adding any livestock. This allows time for nitrifying bacteria to populate your aquarium which will help to quickly process ammonia into nitrite and finally nitrate. A system that has been inadequately cycled will experience a build up of ammonia and ammonia can quickly become lethal to all of your reef tank inhabitants.
In this article we will discuss "Nutrients" and by that are sole focus will be strictly on Nitrate and Phosphate. It mostly goes without saying that an aquarium must be appropriately cycled before introducing livestock. If you need more information regarding cycling a new reef tank, stay tuned, we'll have more articles posted soon!
Nitrates are the end result of the nitrogen cycle in your Reef Tank. When organic matter decays, or when fish eat and poop, ammonia is produced. That ammonia is extremely toxic, but a properly cycled aquarium with a healthy population of nitrifying bacteria will quickly convert the ammonia to nitrite, and finally nitrate which then acts as a fertilizer for the growth of many organisms.
When we talk about "Nutrients" in Reef Aquaria we are almost always talking about Nitrates and Phosphates and not ammonia or nitrites.
Nitrates are sometimes referred to as Nitrogen, as in the Nitrogen cycle, however most test kits and measuring devices will be displaying the results as nitrate. There are converters you can find online to convert nitrate reading to nitrogen and vice-a-versa, but we don't think that's too important overall.
Phosphates are sometimes referred to as Phosphorus. For Example, Hanna's ULR Digital Colorimeter can measure results as phosphorus ppb (parts per billion) and must be converted into phosphate ppm (parts per million). They provide a chart, but you can also find calculators online to do these conversions for you. Most people are interested in phosphate ppm and not phosphorus ppb.
For testing, we recommend keeping nitrate simple with a Salifert Nitrate Test kit (simple, easy) or something like a NYOS nitrate test kit. For phosphate, we need to get more accurate at smaller concentrations so we are really going to want a digital tester. We recommend using Hanna Phosphorus ULR (Ultra Low Range which will give you reading in phosphorus ppb, and a chart to convert that to phosphate ppm (Multiply ppb phosphorus by 3.066 then divide by 1000 to equal ppm phosphate)
These nutrients are important building blocks for all organisms in your Reef Tank and it is essential that you keep them present and available in your system (test daily, feed a lot, and balance your filtration.) You can read more in our Feeding, Filtration and your Reef Tank.
NUTRIENT IMPACT ON CORAL GROWTH
Nitrates and Phosphates are required by corals to grow, and elevated stable nutrients in your reef are critical to long term success. As with most things, stability is key rather than a specific number, but we always like to see our nitrates at around 5ppm-10ppm. For you, that might be 10ppm-20ppm (although at lower numbers you are closer to hitting zero than you realize.) Some folks may even experience success at higher than 20ppm nitrate depending on the species of corals kept. Most would advise that you aim to keep them below 20, however.
A lack of nutrients in the system will lead to bleached out and eventually dead corals. A nutrient starved system will see an immediate impact on the health of its inhabitants upon heavy feeding of organics or even dosing of inorganic forms of Nitrate and Phosphate. At Reef Chasers we prefer to use organic feeding as the means of increasing nutrients, as this is the process most similar to natural reef formations. We will still use inorganic dosing as a "back up" in times of need. We often do not dose anything upon an initial test result and instead wait to confirm those results 2 days in a row before taking any corrective action. The reason behind this is simple: some days we get bad test results and the next day the system is perfectly fine and back to normal with no action necessary. Imagine if we took action every time we got a single result that was off? Talk about instability!
NUTRIENT IMPACT ON NUISANCE ALGAE
It was once thought that nuisance algae infestations were the result of 'too many nutrients' and that some how one could starve the algae out by reducing the nutrients. HA! Good luck with that one. The honest truth is that you will easily starve every other organism in your aquarium before you ever starve out the algae. This is true for most of the edge competitors as well like Dinoflagellates and Cyanobacteria. A starvation strategy NEVER works, often makes matters much, much worse, and before you know it the only thing left alive in your reef tank is the very thing you were trying to wage war against.
Instead, a better strategy is to maintain stable, slightly elevated nitrate balanced with the phosphate. Typically balanced nutrients involve the phosphate being very low and the nitrate much higher, such as 0.1 ppm phosphate and 10 ppm nitrate. If phosphate is allowed to rise, or worse, nitrate allowed to plummet then you will likely be encountering something like Cyanobacteria soon (we seem to see heavier infestations of Cyanobacteria be more prevalent when Phosphate is out of Balance and higher than it ought to be or nitrate has fallen to near zero levels while phosphates remain elevated.
Maintaining elevated, balanced nutrients over the long term yields good results in battling Dinoflagellates and Cyanobacteria as well as algae. The reason for this is that you are creating a healthy reef environment that is now capable of allowing other organisms to thrive and not just the unwanted edge competitors that can survive on literally nothing. Over time, your aquariums population of microorganisms will become more diverse, and eventually the edge competitors will lose out to other organisms. When you starve your aquarium of nutrition you create the exact opposite conditions. No other organisms can survive at all and they are thoroughly out competed for what little nutrients exist by the undesirable algae and bacteria.
NUTRIENT IMPACT ON CORAL COLOR
We already know that nutrients can affect the overall health of your corals. Healthy corals almost always produce brighter, more vibrant colors than stressed or unhealthy corals. But when it comes to certain species of corals, namely Acropora spp., Nitrates can have an affect on what colors the corals actually produce. Most corals are not like this, but with Acropora when people are running high nutrients it is advised to blast the acros with far more lighting than might otherwise be required. Sometimes this means getting par levels as high as 800+ for Acropora. This can lead to dramatic displays of color among this species. If nutrients are high but appropriate lighting is not provided, then you may see otherwise beautiful Acropora turn dull and boring brown. This is called "Coral Browning" and is typically only seen with Acropora type corals. If your nutrients are high then it is recommended to blast the Acropora with light. In these conditions, you may see new colors not seen before, or rainbow-like coloration effects. Usually with higher nutrients and higher lighting people also like to keep elevated Alkalinity for Acropora. This will help skeletal growth keep pace with tissue growth and prevent 'burn tip' phenomenon. There is a very unique and interesting interaction happening there between Nutrients, Light Power, and Alkalinity that is not fully understood and seems to only really affect Acropora corals. Likewise with lower nitrates, less lighting and lower alkalinity you can also achieve great results with Acropora Coloration. Keep these interactions in mind while balancing your nutrients, especially when keeping Acropora.
ORGANIC VS INORGANIC
When we talk about nutrients like Nitrate and Phosphate in your Reef Tank there are two ways to introduce them. Organic sources and Inorganic sources. Organic sources such as Food lead to a natural organic decay that results in Ammonia and the triggering of the nitrogen cycle. Food also is eaten by your Fish, processed through digestion and ultimately deposited into the water column and to your corals. This also results in ammonia and the triggering of the nitrogen cycle. Feeding is the best way to increase nutrient levels in your tank. It is a wholly organic process that closely mimics what happens in nature. We feed meaty foods, flake foods, pellet foods and especially phytoplankton to all of our reef systems daily. Other organic sources could be dead or dying livestock such as a dead fish deteriorating in a dark corner of your tank, die off from live rock which can be disastrous to a brand new system, and/or die off of algae. When battling an algae infestation, if any chemical approaches are taken you can expect the die off to increase nutrients in the short term.
Inorganic sources would be dosing liquid Nitrate or Phosphates sold under common brand names these inorganic sources can be used as a tool in your belt for helping push your nutrients into desirable ranges or any time "feeding" doesn't seem to be getting the job done or not done quickly enough. We would typically only recommend this after you have already tried natural feeding methods or in the case of an out-of-balance parameter as organic sources will tend to introduce both Nitrate AND phosphate while you may only want to supplement one or the other. In these cases, inorganic dosing of nitrate and phosphate is recommended.
We cover this topic in much more detail in our feeding and filtration article but we will touch on it here. There are many mechanisms to export nutrients from the system but they are best thought of in three main categories:
- Chemical Filtration (things like organic carbon dosing and lanthanum chloride)
- Mechanical Filtration (Things like Skimmer, Filter Socks, Denitrators, and Activated Carbon, GFO and WATER CHANGES!)
- Biological Filtration (Bacteria, Macro Algae).
Hobbyists can implement a combination of all three of these to retrieve proper filtration and nutrient balance. Most of these mechanisms can be throttled in one way or another and it will take a little tinkering for you to figure out the correct balance. It's important to not OVER FILTER the water column which is certainly possible this day and age with all of our fancy, high tech equipment, knowledge and available resources.
Although for most hobbyists the first line of defense is weekly water changes. Often times a sock, a skimmer, and a refugium will be implemented as well based on the size of your aquarium you may use some or all of these. Regardless of aquarium size and filtration equipment you can always lean on some organic carbon dosing or lanthanum chloride when a little extra cleanliness is required. We prefer to only use lanthanum chloride (sold under the common brand name Phosphate-E) as a last resort when phosphates are climbing rapidly to undesirable levels. In these circumstances we will likely opt for heavier water changes as well.