Nitrates In Reef Aquariums
by Justin Hester
Nitrates in the reef aquarium have always been a bit of a moving target. They fight for notoriety among the other parameters we monitor for coral health. Testing for them has in short been a pain and with all the new reef technology that’s come out lately, testing for nitrates is only starting to get some marginal love. For the most part, testing for nitrates still involves relying on veru subjective color titration kits that don’t give a definitive reading Adding to that frustration, is the myriad of ways to deal with removing nitrate from your reef aquarium even if you are even able to determine that your levels are too high. Let’s check out a couple of the most popular ways to deal with nitrate in our reef environments and see how they compare as far as efficiency, cost, and maintenance.
What Are Nitrates?
Nitrates are organic molecules that enter our aquariums via fish food as well as via the final stop on the Nitrogen cycle. In the last phase of Nitrification, Nitrates are taken up by plants that use them as food as well as by denitrifying bacteria that reside in anoxic places deep in the sediment. Interestingly, both of these processes are the basis for the most popular ways we remove nitrates in our reef tanks.
In reef tanks, nitrates are necessary in small quantities to fuel the photosynthesis. This then gives our corals the sugars they need to grow and create skeletons. In large quantities however, nitrates can fuel massive growths of algae that can smother and compete with corals for real estate on the reef. Some of these algaes even compete for light with our corlas by releasing compounds that can sting our corals, like other corals can sometimes do.
Testing For Nitrates
Unfortunately testing for nitrates still remains a royal pain. To date, there is not a cost effective method on the market that provides a spot-on reading. There are however there some promising devices coming onto the market in Europe as we speak. Like most of the parameters we try to maintain in our reefs, having good testing data to compare and make decisions with is very important. The day a device comes out that makes testing for nitrates as easy as say alkalinity is with the Hanna Checker, I think people will pay closer attention to nitrates as a whole in their reef aquariums.
Nitrate Removal With Carbon Dosing
Carbon Dosing, aka Vodka dosing, the name sounds so technical that it almost entirely robs your brain of the reality. Can’t you picture a group of discerning reefers that decided to share a friday night toast with their reef tank? In reality, the concept is pretty genius. Culture bacteria that consume nitrate by adding a carbon food source for them to grow on in your reef aquarium. People have tried carbon sources ranging from vinegar, sugar, acetone, and the most popular, vodka. You start with a small amount of carbon dosed into the water daily and then ramp it up as the culture of bacteria grows. These nitrogen laden bacteria can then be permanently exported from the reef aquarium by your protein skimmer. People who use this method on their reef tanks report a positive change in water clarity, an increase in coral polyp extension, and a general pastel color shift in their coral’s tissue.
The efficiency of this method depends on what you measure efficiency by. As far as removing nitrate from the water column, the bacteria definitely achieves this. Removing that nitrate heavy bacteria from the tank is then then task at hand. Some protein skimmers are better than others and this is what determines how efficiently carbon dosing will work for your system.
Another popular way to achieve carbon dosing is with bio pellets. These achieve the same nitrate removal as carbon dosing, but with one benefit. The bacteria are housed in a chamber called a reactor which makes them easy to remove. For removal, all you simply need to do is direct the exit tube of the reactor right into your protein skimmer. The protein skimmer then removes these nitrate laden bacteria from the reef system in the skimmate collection cup.
The cost of this method can vary depending on whether you are using your favorite cheap vodka, or a reactor holding media pellets. The later being a recurring cost that depends on the size of your tank to maintain. If you are using the vodka dosing method, your cheapest plastic bottle vodka is perfect for the job.
Maintaining a Carbon dosing regimen is pretty easy since all you need to do is add more pellets or vodka depending on which method you are using. If you are using bio pellets, sometimes they can get stuck together which just requires an increase in flow to separate the little pellets. They even offer a new style of pellet which is larger and thus less prone to clogging. Check out a full dosing regimen discussed here.
Removing Nitrates With Chaeto
At ReefNation, we try to opt for the easiest ways to keep our tanks happy and nitrate removal is no exception. We have taken the idea of a refugium and fashioned it with Chaetomorpha a brillo like algae that grows in a cork screw shape and doesn’t have any roots. This stuff grows in a nice tight
ball and all you need to do is remove a handful of it to remove nitrates since the plant uses these nutrients to grow. Since it doesn’t have any roots, this is easy to do by just pulling apart the strings and tossing it in the garbage. Using this method not only helps with nutrient export, but allows you a safe haven to grow a ton of amphipods and copepods. By far, this method is the cheapest route and simplest to maintain. All you need is a spot that has some light and flow where you can stick a handful of chaeto and watch it grow.
Nitrate reactors are a bit of an anomaly when it comes to reefkeeping equipment. I have to admit, i’ve seen them in reefkeeping catalogs or on websites for years, but I’ve never put much thought into what makes them work. It turns out that these devices actually capitalize on one of the same denitrification methods that exists in nature, namely anaerobic bacteria that usually live deep in sand beds. There seem to be 2 main designs on the market for these devices, one being DIY and the other being a 2 chamber reactor.
The first design is a simple device which one of our local reefers Bruce recently built out of a cylinder and some tubing. The premise is that the water slowly corkscrews through the tubing which is wrapped around the cylinder. As this water travels down the tube, all the air bubbles are released, making the water anoxic as it passes into the cylinder. Inside the cylinder is sulphur media which serves as a home for the denitrifying bacteria. Water is fed very slowly through this apparatus and as it passes through, nitrates are stripped out by the bacteria. The system is pretty simple and inexpensive to setup and maintenance is virtually nothing after that. The only downside to this device is that as the water comes out, it will be fairly acidic due to the chemical reactions that take place inside the reaction chamber.
If what you are looking for is a ready to use high volume production version of a nitrate reactor, there are several models out there to choose from. They range from a couple hundred dollars to some of the larger units that are well over a thousand. The basic design is the same as the DIY model with a couple of exceptions. These units add a second chamber after the main sulphur media chamber that houses calcium carbonate. The thought here is that the acidic nitrate free water from the sulphur chamber will pass through this second chamber here and be buffered back to a higher pH before it is returned to the tank. These units also usually are packaged with some type of pump although some of them are gravity fed.
The method you choose to remove nitrates from your tank isn’t as important as the removal itself. Pick the method that best fits your budget and attention span and stick to it. Hopefully some of these options give you a few ideas on the various methods so that you can choose one. If you have any variations on these, we would love to hear your experiences.
Justin has kept and maintained marine aquariums for over 20 years. His love for everything coral led him to start ReefNation in 2010 which aims to inform others about the world’s oceans as well as provide sustainably grown corals to the reef aquarium industry. ReefNation currently grows over 150 unique corals in their 3 aquaculture facilities.