You can try to return it or just keep it and feed him once a week with a "snack" in the middle of the week. I have a 13" RTC, he was 4" when I bought him and had him in a 55, within 5 months he's tripled in size, I used to feed him feeders just for the thrill then realized potential diseases because I used to have oscars and only pellet fed, so I stopped and now feed him smelt, tilapia, beef heart, chicken liver, occasional piece of lunch meat or hot dog, I've fed him venison which they love. 2 months ago I got him a 125g hoping he can Atleast get through the next year so I can get a new house instead of apt and build a 2250 gallon indoor pond. I have baby rtcs, tsns, and hybrids growing that are being power fed to go in the pond as well without a problem!