Hi all. My brother got a betta recently and I'm trying to get him on the right path. He currently does not use a filter in there and does 80-100% water changes using a no-name tap water conditioner. I recommended he switch to Stress Coat Plus but no biggie if he doesn't as long as what he has works. I've also recommended a heater to get the water temp up. I'm now wondering if he should get a small internal sponge filter. Is that recommended? If so, are there are any specific models that are widely used and liked? Particularly for bettas, I'm looking for one that doesn't cause too much flow. Links appreciated!