Assuming this tank is at least 5 gallons:
Good tankmates: Dwarf African Frog, Common Guppy (not fancy), White clouds (excellent), Harlequin Rasboras, Cherry and Gold Barbs, Large Neons and Glolites, Large Ghost Shrimp, clown loaches, corydoras, non-brightly colored livebearers (if they're too bright, a male might mistake it for another betta, which I why I said no Fancy guppies.)
For Algae: Siamese or Chinese Algae Eaters are ok WHEN THEY ARE YOUNG! As they get larger, they get more aggressive. Plecos are placid and good for a large tank, but a fish that is excellent but overlooked is the Otocinclus. A cute 1.5" algae eater & Scavenger that is gentle. A group of 3-5 of these inexpensive fish will clear up algae quickly. Also, mystery/apple snails are excellent and do not multiply rapidly if you only have one.
be creative...just don't overcrowd and monitor carefully.