I have bushynosed plecos in all my tanks even my small 6 gal. It's a baby less then 1". I have a friend that breeds them so I can get the tiny babies. She might be ok as long as it's a baby one. They seem to grow very slowly and I even had one in a 3 gal. to keep the algae clean off of that tank. They are very good at keeping the algae and food off of the bottom of your tanks. I have not had to much luck with the Oto cats. I figure if they grow to large they are easy to rehome on craigslist my biggest baby is in my 55 gal. and it is only about 2" the other BN pleco in with that one is about 1". I also have a 1" BN pleco in my 10 gal. tank.Good fish stores will carry baby BN plecos. My friend has so many that she can't keep up with all the babies being born. She sells them at The San Diego Tropical Fish Society that we both belong to.
Snails will be a big problem with a betta because they are so slow moving over a active BN pleco. Bettas can be really mean so you have to watch what you put in with them.
You can alway just use one of those algae scrapers or magnets to keep the algae clean and not have you lights on for a long time to control the algae.I have all my lights on a timer for all my tanks 9 hrs but I have live plants in all my tanks so I need them on for that long.