Mastering Freshwater Aquarium Ecosystems
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Nitrogen Cycle (Cont.)

Hydroponics system can also be added to an aquarium ecosystem to control and reduce nitrates.  Hydroponics system method may be the best for aquarium systems that have a high bioload like tanks with large cichlids, and growout tanks.

A substrate comprised of fine sand can also help with denitrification. Anaerobic bacteria live in areas devoid of oxygen. Anaerobic bacteria use the oxygen attached to the nitrate freeing up nitrogen gas that then can escape into the atmosphere. Anaerobic bacteria will colonize the depths of a sand bed. Using Malaysian live bearing snails (Melanoides tuberculata) to slowly turn over the sand bed will help exchange nitrate rich water through the sand to the anaerobic bacteria. Catfish from the Corydoras genus as well as other small sand sifting fish can also help get nitrate to the anaerobic bacteria.

Panda Cory

Panda Cory (Corydoras panda) is used in this aquarium to turn over the sand to aid anaerobic bacteria in nitrate reduction.

It is recommended that you have at least a 1 ½ to 2 inches (3 to 5 cm) of fine sand. Gravel allows the exchange of oxygenated water to cycle to easily through the substrate for it to be useful for NNR without requiring a significant depth. The finer the substrate the shallower the depth needs to be to achieve some denitrification. The pH also affects anaerobic bacteria population. To maintain a healthy anaerobic bacteria population the pH should always be kept on the alkaline side, as they do like acidic water.

New Tank Syndrome

When fish start to die in an aquarium that has been set up for less than a month, it is often referred to as “New Tank Syndrome.” Toxic levels of either ammonia or nitrite are what causes new tank syndrome in an aquarium that does not have an established nitrogen cycle. Typically, if fish show stress or start to die within two weeks or less, it is a toxic level of ammonia. At two to four weeks after the aquarium is set up with fish, it is typically nitrite poisoning causing stress and mortality.

When you start a new aquarium, it takes an average of 35 days at 82° F (28° C) to develop enough bacteria in your aquarium to keep your ammonia and nitrite levels near 0 ppm. After adding the first fish, ammonia levels will normally peak around two weeks, and nitrite levels will peak around three weeks. During the first month you should keep the fish population very low. The more fish you start with the higher your ammonia and nitrite levels will go. Also keep your feedings light and only once every other day. Your fish will not starve to death, but you could kill them with too much food in an aquarium that does not have an established nitrogen cycle.

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