Oh I'm in love with my nerites too!
I have two in my community tank ( very peaceful guys in there with just danios and ghost shrimp) and two in my 5 gallon with Miz Bea. She is another extremely
territorial betta who refuses to live with anything else at all, but is doing fine with the nerites. I ordered mine from ebay, and I ordered the horned, or spiked ,variety. Sure enough, when they first went in she bumped one but got stung a bit!
Now she totally ignores them and it's been several months. She's a bratty betta but not a dumb one, lol!
The guy I ordered them from sent two extra ( I ordered two) which is how I came to have two in the community tank. I actually don't have much algae in there, and the two in my betta's tank quickly cleaned up what was there.... I drop a couple of bits of algae wafer in every few days, the snails seem to go for it after a day has passed when it's softened up. I also "grow" some algae rocks in a tub for them
(My 5 gallon is a Fluval spec 5 with the center of the lid cut out but the snails have never tried to climb out btw)
They are so worth the trouble !!