Nitrate in Aquariums | Suite101.com

Most aquarists are aware of the biological cycle of aquariums. In this cycle, ammonia is transformed to nitrite, which is then broken down into nitrate. This is the most important cycle in the aquarium and should be understood by those who are interested in keeping their aquarium in good shape (a detailed description of this cycle can be found in one of my earlier articles, "The Biological Cycle: A simplified explanation ".). Most aquarists figure the cycle stops with nitrate. The truth is that in fresh and saltwater aquariums nitrate is the end of the process. As a result, nitrate builds up in the aquarium over time until the next water change. Luckily nitrate is not harmful to fish when in normal concentrations. The case is somewhat different for reef aquariums.

Reef aquariums are unique since they contain invertebrates. Unlike fish, many invertebrates are not tolerable to high nitrate concentrations. As a result, it is extremely important to make sure that nitrate levels do not reach high levels. To do so, one either must do frequent water changes, or try and eliminate sources of abundant nitrate generation. Recently there has been a drive for reef aquarists to avoid trickle filter systems. This is due mainly to the large nitrate levels they can promote. Trickle filters are wonderful for saltwater aquariums since they provide a large surface area for nitrifying bacteria to colonize. This is wonderful for maintaining a healthy saltwater aquarium, but the tradeoff is fast nitrate accumulation. Thus, many reef aquarists have turned to sump boxes and even just simply a protein skimmer.

So, what should one do? Luckily there are a few ways to avoid excessive nitrate buildup. First, if you already have your reef system together with a trickle filter, please do not go out and replace it. Rather, you can simply do your best to maintain regular water changes, and make sure that you test the nitrate concentration. By far, water changes are one of the easiest ways to avoid excessive nitrate.

If you still seem to be accumulating excessive nitrate, you may want to consider a live sand bed filter. These filters are specifically designed for denitrification. I am not a big fan of live sand filters, but they have been shown to be very beneficial. If you are considering using no filtration or a simple sump box design sand filters may also be something you should look into.

The other big producer of nitrate is excessive live rock. This requires a little explaining. Live rock contains photosynthetic organisms that have the potential of conducting denitrification (the breakdown of nitrate into nitrogen gas). This is a wonderful thing since reef aquariums can actually remove nitrate from the system. Many think this means that one should have a lot of live rock so that the reef system can break down larger amounts of nitrate and thus avoid accumulation. This is not the case. When excessive live rock is used in an aquarium, "dead zones" are produced where water flow is insufficient to support the photosynthetic organisms. Also, it can be difficult to get light down to these organisms since the reef structure is too dense. As a result, the quality of the reef aquarium suffers and nitrate buildup continues as usual. So what is the proper amount of live rock? The correct amount of live rock for an aquarium should be 1.5 to 1.75 lbs. per gallon. Any more, and dead spots will occur. If you try and follow this simple rule of thumb I can assure you that you will be very happy with the stability of your aquarium.