they work well, or at least during the vacation i took i didn't come home to any headless cichlids. 2 years ago i unwisely took a 3 day trip and didn't leave any method to feed my fish, when i returned home i found may GT floating with no head, probably fell victim to my O. a few months ago i went on a 5 day trip before leaving i drop a few weekend feeders in my tank when i returned home there were no casualties mind you that i have a tank with O"S, RD, Mang, Mota, Texas, Uro, Channel cat and a Pleco so i guess they work