Aquarium Filters
Aside from aeration, filtration is the best aid to a "balanced" aquarium. Not only does it eliminate solid waste particles floating in the water but, with the use of activated charcoal, it helps to remove the harmful gases dissolved in the water. Filtration is also very useful in aiding the circulation of water.
The mechanics of filtration are easily understood. A filter system is set up so that water is forced to pass through a straining device—usually filter floss or sand, or both—to remove solid debris, and then on through some activated charcoal to remove the dissolved gases.
The advantages of outside and inside filters are open to debate. About the only great advantage the inside filter has over the outside filter is that should the filter fall from the tank or develop a leak, the water will not continue to run out, as in the outside filter, until the siphon loses contact with the water. The inside filter, however, occupies more space than the outside filter, and will crowd the aquarium a little and be rather unsightly.
Cleaning of the sand and floss is easy. Merely run hot water over the sand for a few minutes to get all the dirt and debris out of it. The floss should be changed. To recharge the activated charcoal, you need only to cook it on the stove for 15 or 20 minutes. Filter stems and return stems should be cleaned periodically with a brush made just for this purpose.
Undergravel filtration, a principle that was responsible for a major boom in the aquarium hobby, was invented by Norman Hovlid. The Hovlid principle is in placing a flat plastic slotted tray under the gravel. The tray has about a one-fourth-inch space between it and the bottom of the aquarium. Water is drawn through the gravel by means of the filter and returned to the top of the aquarium.
The great advantage of this type of filtration is that there are no messy filters to be cleaned and floss to change.
