This is my first betta. I have him in a 2 gallon 360 aquarium that has an undergravel filter and an air pump that goes up the middle. The undergravel filter is basically just a piece of plastic with holes like a strainer, that I have gravel on top of. It seems like that won't do much so I added an elite mini underwater filter that I stuck to the side of the tank. My question is, do I really need it? My betta seems to not be swimming around as much now that I put the filter in and I think it might be because of the filter. I'd rather not use it at all but I don't want the water to get too dirty. Any advice?