Does a 2.5 gallon fish tank need a filter?

It's a betta fish tank that's designed to hold two male bettas peacefully by having a divided placed in the middle. I installed the filter provided with the kit but it seems to create a much too strong current for such a small tank. It causes problems for the fish sharing the filter's side of the tank. The water surface per fish is 4" by 5" without the filter, but with the filter(the cartridge plate lays flat to keep the filter body and tube from touching bottom I assume) the fish it sides with is downgraded to only 1" width with the same 5" length at the water's surface. Realistically it can only come up for air(as they constantly do) and water in a 1"x1" section because if it nears the other 4x1 section it gets thrown against the divider due to the strong current. I've read that I'll kill the bacteria and then the fish if I turn it off, but I've only had it for 5 days so I doubt there has been much vital bacteria growth yet anyways. So is it ok to turn it off now for good and treat it like typical .5-2.5 gallon tanks(or a fish bowl) that don't use filters at all? Thanks for your time and knowledge.