One of the principal waste products of marine fishes and invertebrates and the main nitrogenous substance resulting from the decay of plants and animals is ammonia. Ammonia is a colorless gas. Some of it escapes into the atmosphere but most of it remains behind to be oxidized by bacteria to nitrates and nitrites. Some of these bacteria are found inside the aquarium while large numbers turn up in the filters where the wastes accumulate. If the bacteria are plentiful enough the ammonia will be eliminated. Unfortunately nitrites are thought to be the cause of respiratory problems in marine animals, particularly in invertebrates. They also act as fertilizer for unwanted algae which invade the marine aquarium.
It is possible to remove much of the droppings with the aid of a diptube or bottom siphon. They can be decreased by feeding sparingly and making sure no uneaten food remains in the tank. This is often impossible to do or too time-consuming for the average aquarist.
The filter is one answer to cleanliness in a marine tank and it should be selected with this job in mind. Use a filter which whould be slightly oversized for a comparable fresh water tank. For example, a filter which would be used in a 20-gallon aquarium with fresh water would be about right for a 10-gallon marine aquarium. A good sized filter is important because it can handle a large volume of undesirable wastes and at the same time create a small current in the aquarium.
Some people do not choose between an outside or sub-sand filter; they use them both. Others have 2 outside filters, one at each end of the aquarium to assure better cleaning action. Inside filters (not the sub-sand type) are not as good as the outside variety, are difficult to clean, and take up the valuable space in the tank.
The usual filtering medium is a marine aquarium is a layer of charcoal topped by glass wool. A good filter will remove many of the wastes from an aquarium but remember, the wastes are in the filter and as they break down, they can return to the aquarium by way of the filtered water. To completely get rid of the unwanted material the filter medium must be cleaned as often as possible. In addition, changing some of the water in the tank periodically will help prevent the build-up of the various metabolites.
It goes without saying that only plastic (no metal) filters or filter parts should come in contact with the sea water.
BIO-Wheel power filters can be used for freshwater and marine aquariums. The power filters offer mechanical, chemical, and biological filtration; eliminating toxic ammonia and nitrite on contact. No pumps, valves, or tubing are required. Never clogs and never needs replacing. Each power filter comes with a Penguin filter cartridge filled with premium activated carbon. The improved BIO-Wheel power filters utilize current, upgraded Marineland Rite-Size cartridges. Manufacturer offers a three year performance warranty.