Algae eater?

[busdriver]

Well, I'm back, after almost ten years, my daughter and grand daughter got me involved with a fish again.
They bought me a betta for Father's Day.
Now this betta is spoiled and a picky eater, so far, it doesn't seem to like any of the recommended food for bettas.
The reason he's spoiled is because his owner keeps buying him different sizes of tanks.
He came to me in a little bowl which changed to a plastic very small fish tank, then that was changed to a
5 gal. Fulval Spec V and now he's going to be moved into a 15 gal Fluval Flex.
My question is, as a former (accidently) breeder of bristlenose plecos, what kind of algae eater (no snails)
can I put in with the betta?
I'm planning on purchasing about five pygmy cories as bottom feeders.
I would really love to get a pleco, but if it's not possible, well.
Any suggestions?