Apple snails/mystery snails they are HUGE and poop a lot!!! Also, certain bettas harass them for the feelers (looks like food!).
I've decided to "trade in" my big snails for ramshorns. These snails reproduce easily, so it will add to my betta's diet; the ones too big to eat can clean the tank.
I got 6 teeny ramshorns (for free) when I set up my 5 gal w/ 2 baby girl bettas. After the 1st day, I never saw one of them again. Yum! Crunchy snail!
4 bettas: Butch, 3-year-old violet male PK EE & 3 girls in a 30 gal sorority. I do not name the girls anymore! 1/2 of them die within a month.
30 gal: 9 Oto cats, 4 Ocellifer cats. Inverts: Cherry shrimp & 2 assasin snails.
10 gal.: Butch, his 5 oto cats, 3 assasin snails, and a few snails the assassins haven't caught.