Beta fish are a huge range of species - I'm guessing you mean a Siamese fighting fish male - you can see why their name has been changed!

He will be fine with other fish that do resemble him in colour or finnage - plecs will rapidly outgrow your tank and all algae eaters can do very well with algae wafers - get online, visit dedicated fish sites and ask advice from other fish stores.

Plecs are out of your range with the size of tank you have, very small fish are likely to be bullied by your Siamese and larger fish will tend to nip his fins in such a small tank.