Nitrate

Your first exposure to nitrate will occur near the end of your initial cycle period. Bacteria colonies form to change ammonia to nitrite. Then new bacteria colonies form to change nitrite into nitrate.

Levels in your reef aquarium should be kept below 10 ppm (parts per million). Fish can usually tolerate levels above this but many corals cannot. This is another reason why you should not add any animals to your reef before the cycle is completed. Some will needlessly die if you don’t wait.

Another problem with high levels is nuisance algae growth. It is a plant fertilizer and many forms of algae will really take off it accumulates in your aquarium.

Try to find the cause of your high levels and eliminate it. Is it your water source? Is there something dead in the tank that you cannot readily see?

Are you using a filter sock on the intake to your sump? People use one to quiet down the noise from the rush of water into the sump. If you are using a filter sock, it needs to be rinsed out a few times every week or it will become a nitrate factory.

If you are using bio balls, start removing them slowly. Take a few out each week till they are all gone. They also become a haven for unwanted nutrients. If you remove them all at once, too many bacteria will be removed with them and you may start a cycle again.