QUESTION:
I am looking for a filter for my small betta tank, it is about 3 gallons. I have been told that sponge filters are a good filter here, but I also was told about under gravel filters. Also are there differences in brands?
ANSWER:
Sponge filters excel as small tank or bowl filters, they fit nicely in small spaces and are cheap to own and maintain. For a betta, there is no better filter in my opinion. They are excellent bio filters and good mechanical filters in small aquaria.
In fact, a sponge filter is probably the best choice of filtration for breeding tanks, Betta tanks or bowls, hospital tanks, and even discus aquariums, due to the fact that they do not "suck" in baby or weak fish or attract noxious bacteria.
Sponge filters are one of the best biological (and unfortunately most under rated) filters in the hobby that is often driven by anecdotal evidence. One myth, Bio Wheels and Wet Dry filters are superior to sponge filters is not true when one moves from theory to actual tests and evidence
In theory the added oxygen or bio wheels and wet dry filters is great, but in practicality the channeling of wet dry filters and the deposit build up of Bio Wheels lowers bacteria surface area, while the fact remains that with the proper dissolved oxygen levels your fish should have is more than adequate for a healthy sponge filter to maintain proper bio colonies. I have performed side by side tests with sponge filters in my service business and the sponge filters out performed the bio wheels when ammonia spikes were measured.
As for under gravel filters, there are small ones made for bowls or small tanks, but they take more maintenance than sponge filters (debris tends to collect under the plate). UGFs are more difficult to clean in small aquaria, as they are best maintained by vacuuming, which is difficult in bowls or small tanks.
The brand sponge filter I would recommend is the Hydro Sponge Filter by ATI (Lustar), they hold the best patents for sponge filters and have many patent infringements to prove it. The sponge material used by Hydro Sponge can trap vastly more aerobic nitrifying bacteria (for ammonia, nitrite removal) than their nearest rival. I have used many others (including homemade) and they are not the same.
