Types of Filters
Another popular filter that often is also packaged with a new tank is a box filter. The box filter is filled with filter media like floss to trap the solid waste. Bacteria will also grow in the floss and aid in ammonia removal. You can also add other types of filter media to encourage more bacteria growth like the Fluval Biomax Bio Rings shown to the right. Put the rings in the bottom and still top the filter off with the floss. An air hose will attach to the filter and also a pump to drive air into the filter. A current is created through the box pulling your tank water through the filter media and trapping particles. These are great filters for a Betta tank as long as you do not get a big pump that will cause a lot of current. And these filters are also very easy to maintain. Once a month, during your water change, remove the filter floss and rinse in used tank water or water you have treated with dechlorinator to get the solid particles out of the floss. You do not want to use chlorinated tap water as it will kill of the bacteria you have been trying to establish. If you use additional media you just rinse it the same way to remove the solids that are decomposing in the tank.
Under Gravel Filter
Under gravel filters are another type of filter and tend to work best with bigger tanks. This filter is a plate that sits on the bottom of your tank and has holes all over the surface of it. You place several inches of gravel on the top of the plate, and attach tubing to the air stone in the uplift tube. The other end of the tubing is attached to a pump that pumps air into the tube. As the air rises, it creates an upward current that pulls the tank water down and through the gravel. It turns your entire gravel bed into a big biological filter. A gravel bed offers a tremendous surface area to grow a lot of bacteria, but having a lot of the organic matter down in there can actually cause you more problems. Decaying organic matter will affect your water quality unless you have a siphon tube that will "vacumm" your gravel and remove the funk. As long as you do weekly gravel cleaning, this filter can handle a well stocked tank. Because you are pulling a lot of organic mater into the gravel, this type filter is not the best if you want also to grow aquatic plants. High organic loads in the gavel will cause your plants rot. Because of the maintenance involved with this filter it is best to avoid it's use with your Betta.
The choice of filter you chose to use is going to depend on several different things. The size of your tank and the boi-load or the number of fish you will be keeping per gallon. For a single small tank with a Betta or two the sponge and box filters work best. If you are breeding Bettas, larger tanks are used for growing the youngsters out. In larger grow out tanks, a big sponge filter is the filter of choice for most breeders. Selecting and maintaining a good filter will go a long way towards keeping your Bettas healthy and their water quality good.