I have a new betta in one of my heated goldfish tanks with a medium-strong conflicting current (water goes towards the center from the outside to create bubbles into the middle to break the surface). The current grows weak halfway to the tank bottom, its just for surface agitation. The betta does fine. He learned the weaker spots in the tank where he can hang out. I also have caves in the tank where he can avoid the current and they are big enough for him to swim around in. I've been integrating him slowly throughout the week and just yesterday he proved he could compete with the goldfish for food fine. I always make sure they are quick enough to get their share.