I have this same tank...just got it last weekend. It's a nice tank, however I'm new to Bettas and was unaware of their needs so mine is divided between two crown tail males. Not an ideal situation, but so far it's not going so bad. Have you baffled the filter? I've been looking for a way to do this, as the fish on the left has to deal with nearly all the current, but being new to this and all, I'm at a loss!
Anyways, congrats on the new tank! Hope Uva enjoys it!