RayClem said:My premise is that you can never have too much filtration. Yes, a small sponge might work, but it will need to be rinsed often to remove debris so it won't clog up. If you use small sponge filters, you might want to use two of them so you can clean one at a time. Something like this combines two small sponges in one unit.
For a 29 gallon tank, I recommend a larger sponge filter such as one rated for a 60 gallon tank. That way, you won't need to clean it as often. This is what I use.