NOOOO take it out. I had 5 of them in a 50 gal tank with huge koi and they attacked the koi. They are vicious. Keep them out of your tank or you will be scooping up dead fish. The first couple days, they were fine and I thought that it was going to be ok untill the koi started to lose scales and...
Pellets. and when the koi are too small to eat the pellets, it waits untill it turns soggy and then eats it. BUT pellets can lead to cloudy water so I advise you not to over feed your koi with pellets.