Biological removal is achieved by providing the material for healthy growth of nitrifying bacteria within your aquarium. These bacteria convert ammonia first to nitrites and then to harmless nitrates.
They are known as nitrosomonas and nitrobacter.
They can grow on nearly any kind of course material such as rocks, netting, oyster shells, plastic or sponges.
Oyster shells are particularly well suited because they contain calcium carbonate which interacts with other chemicals which helps with PH buffer stability.
These shells are particularly bacteria friendly due to their size and shape for bacterial attachment. The shells' smooth interior prevents sedimentation from forming which in turn clogs up the bacteria colony.
Water should always be treated prior to introduction into the tank to prevent killing or damaging the bacterial beds. Providing a good source of oxygen by aeration is essential to maintaining a healthy biological removal system of unwanted chemicals. The biological beds can only remove what they can chemically change. If the tank is severely polluted, then the system will not work. Good aquarium maintenance is essential so an environment of natural balances can occur and function correctly.
Both sponges and netting can also be added to the tank or filter, providing an excellent medium for the bacteria to attach. These can be rinsed very gently to remove any sediment clogging their surface and returned to the filter or into the tank. Large sponges with aeration wands within them are hot beds for the nitrosomonas to attach and get to work removing the ammonia and nitrite from your aquarium.
Aquatic plants act as a natural waste treatment system. If you have a two-pond system in the garden, excellent water cleansing can occur by grouping your aquatic plants into separate clusters of the same plant group. Allow the pond water to filter over each section separately. Returned water quality will be vastly improved.
Aquatic plants supply both an excellent surface for the nitrifying bacteria to attach, also taking it's own nutrients from the water for growth -- so the cycle is formed. These plants are easily grown in aquariums when proper lighting is provided and adequate substrate is provided for root formation.
Establishing a bacteria population is a slow process.
During the weeks ahead, the water must be maintained as the quality undergoes changes. There will be high ammonia levels as bacteria establish. Oxidation of nitrite to nitrate occurs as levels drop and nitrosomonas work converting.
Do not add fish until cycled. Check water first.