Nitrate Control In A Reef Aquarium
I'm often asked how I control nutrients in my system given that I have high stocking levels and keep sps. I always knew that I'd have a lot of fish in my aquarium and that I ultimately wanted to keep sps so when I was planning the system 8 years ago nitrate and phosphate control were high on the agenda. In my earlier systems I'd tried a variety of measures including vodka dosing and nitrate reactors with good results but bio pellets or pearls were a relatively new product that I wanted to try. They got some bad press in those early days. People with high nitrates saw them as a quick way to resolve the problem, the trouble was pellets are so efficient that nitrate can quickly be reduced to very low levels. For some corals this was just too fast and there were many reports of coral losses after introducing pearls.
Pellets are a form of carbon dosing and the pellets a bi product from the plastics industry require to be tumbled very fast in a purpose made reactor. A media reactor for GFO for example is unlikely to be suitable as pearls need more flow to ensure they tumble effectively with no dead spots. Bacteria form on the surfaces of the pellets which they consume removing nitrates and to a lesser extent phosphates as they do. The effluent from the reactor needs to fed as near as possible to the intake of the protein skimmer which will remove the filamentous slime produced as a result of the process.
To avoid reducing nitrate too quickly I always recommend adding the total volume required for your system gradually over a period of four weeks. Pellets can take between 6-8 weeks to become effective though adding them gradually helps speed this up a little in my experience. Its a good idea to soak the pellets in old salt water or RO overnight so that the don't float in the reactor and clog the intake.
Pellets will need to be topped up every month or so as they are consumed by the bacteria but don't wait until there are none left. You can control your tanks nitrate at the level you want by either increasing or decreasing the volume of pearls you use.
- Jonny Orange