So I got a red tailed shark and 2 swordtails last week for my 29g tank(yes I will upgrade in the future) but 1 of the swordtail died the day i got it, assuming from the store. I read that swordtails are mostly at the top of the tank, so that is why i got it. However it swims most of the time at the bottom and the shark isn't too happy about that so it chases it constantly. Anything I can do to prevent that ?