Lowering Nitrates in a Marine Aquarium
Low Nitrate Levels is Critical to a Healthy Saltwater Aquarium
Dec 17, 2008
It is not uncommon for a new aquarist to successfully cycle a new marine aquarium with live rock and get ammonia, nitrite and nitrate readings to zero. This is good. It is also, unfortunately, not uncommon for nitrate levels to begin to creep back up after a period of months despite consistent daily, weekly and monthly maintenance. Concerned about the elevated nitrates, the aquarist might turn to more drastic measures in an attempt to lower the nitrates, but a series of major water changes and even chemical treatment appears to have no effect. What’s wrong and, more importantly, what can the aquarist do to make it right?
In the above scenario, it is often the filtration itself that is causing the elevated nitrates. Revisiting the system’s filtration and making some changes can result in nitrate levels once again returning to zero.
First Assess Regular Maintenance and Husbandry
Before proceeding with any changes to the established filtration, it is important to take a look at the current tank maintenance protocols and husbandry practices. Elevated nitrates may be a result of poor or inconsistent maintenance (e.g., water changes, skimmer cleaning, etc.) or poor husbandry practices (e.g., feeding too much or using poor quality food). If the aquarist can reduce the nitrate readings through better maintenance or husbandry, that is the preferable approach, but there are times when even impeccable maintenance and husbandry won’t bring down the nitrate levels.
The Problem with Mechanical Filtration
The problem with many systems is that the filtration media itself becomes a sink for nutrients. This is why numerous massive water changes don’t seem to impact the nitrate levels in the system. The newly added water simply gets filtered through the same nutrient-laden filter media, and the aquarist is right back to square one in short order.
In terms of filter media that can be problematic, look out for any foam filter media, filter floss, bio balls, filter socks, or any other mechanical filter media that can trap detritus and other nutrients.
Remove Filtration Media that Traps Detritus
Option one is to slowly, over a period of weeks, remove each filter media from the system (disturbing and removing all at once can be disastrous to the stability of the system). If the aquarist removes biological filtration media (e.g., bio balls), he or she will need to add biological filtration back to the system. It is best to do this with live rock, which is a much better biological filtration method. Don’t add newly purchased live rock to an established system, as you will likely wipe out the entire tank as it cycles. Instead, first cure the rock in a separate container and then add it to the established system once it has fully cycled. In the meantime, consider using a fluidized bed filter for biological filtration.
Regularly Clean Filtration Media
The second option is to plan to keep the same filtration set-up already employed in the system. The difference is that now the aquarist will commit to carefully cleaning all of the filtration components as part of the regular aquarium maintenance. With this approach, it is essential to never clean or change all of the filter media at the same time. Plan a monthly schedule where you clean one component each week (or once a month)—this will allow the biological filtration to be relatively undisturbed. The exception is to clean the filter sock (if you use one) several times a week.
By either removing or regularly cleaning the filtration media in the system, the aquarist should be able to get the nitrate levels back to zero.
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