Doesn't have to be alone; could add some mystery or nerite snails or even a rabbit.
OMG no, do not add a rabbit snail to a betta. I bought two snails not so long ago, thinking the requirements match, betta likes high temp, tylomelania likes high temp, perfect match. NO. almost any betta is a menace, is interested in their tentacles, pokes at them. You will end up with stressed hidden tylomelania and annoying betta. Or mystery snails, same story with the tentacles.
I do recommend neritina though, they have almost nothing sticking out except these hair thin tentacles ( i know it is their eyes guys) and the betta never notices it.
I love this topic, so many recommendations on what to not get or not do. Totally agree.
For me my regret is this betta (and funnily enough the one I had 8 years back as well), while care for him is easy, they should not be kept with other fish, as you end up just trying to merge conditions together and someone ends up unhappy. Had betta with boraras, somehow boraras died (granted they were 4 at that time), added 10 pygmy cories, they disappeared (in a year or so), had a small ancistrus and it disappeared, had cherry shrimp, he ate all of them. Sure, could have been the tank or the green algae I guess, but the betta was always ok. Now he is alone in a 40l with 29°, with a neritina and recently two african dwarf frogs, they work well (except the feeding, have to figure that one out).
I also regret not listening to advice and getting cyprichromis leptosoma in the begging of my large fishtank. I could not get the appropriate numbers cause nobody had them, had only 14 pieces and lost all of them over 3 year span, especially lost all females that had fry in their mouths.
What I never did regret was snails. I read here as people are frustrated with them, but I have had them all and I cant complain! they are a necessary part of the ecosystem, nothing will get rid of a surface film, wood fungus, weak plant leaves,...better than a snail.
I had few mystery snails in the years, absolutely love the color, the behavior and the eye waving. Neritina snails are bit boring temperament wise, good algae eaters, poor things die of hunger in most tanks since they are algae exclusive. Had mine for 4 years now, it is very large and very happy, I even move it between tanks to make sure there is food for it.
Have had malaysian trumpet snails in every one of my tanks that had sand or sand like substrate, I purposefully put them there, even sift through the substrate to get them out and move them and I cannot be happier. They make sure there are no dead zones in the sand, now when I added wood they keep eating the film and making sure the wood is healthy, in their nightly migration to the surface they clean the algae of the glass. I have around 200 by a rough evening calculation in my 360l and it is almost not enough. If you seen my tank pictures, had 12 very massive cryptocoryne with large root system, they never disturbed it, never caused the plants to not multiply, not reach out or have new plants. Same with vallisneria, had a root system with sand instead of a sand (like solid root instead of sifty sand), had mts, no issues plant breeding and no issues with rotted roots or dead spots. I think if you overfeed, sure, they can be a problem, but they are awesome sand helpers.
I was even very unhappy I didnt have any ramhorns in any of my tanks, I have only few (like 10) physa snails and it slowed down nitrification cycle of the new tank significantly (there was noone to eat the film).
I even have clithon snail now, very cute, good worker.
In the end I didnt add the tylomelania to the betta tank, I put them to a different larger almost empty tank where I raised the temp to just 27° (even though 29 would be better, the remaining fish and plants would not agree), and I am so much in love with them I am getting 3 more next week. Never seen more awesome or cute snail, super fun to watch