It's an Otocinclus, Oto for short. They're caught wild because they won't breed in captivity and chemicals are used to catch the Otos. In pet stores they often aren't fed the right thing and so are starved. Supposedly, if they live through the first week with you, they'll last a long time. They only get 1 or 2 inches max and your betta will be fine with it. Good luck with it!