Hello to all and thank you for your replies. We know we are going to have to upgrade to a bigger tank, min size for the 5 Oscars is about 130-150. that should be sufficent according to every pet shop we have consulted. As for feeding them feeder goldfish, I have been a fish enthusiast for years and i know the chances i take with feeding them feeders, i do vary the diet with bloodworms, daphnia, krill, brine shrimp, glassworms and such.....My Main question was about Why my one Oscars colours change lighter and her fins flare up when i introduce the larger type feeders, she has no issues with rosy reds, neon tetra, danios and such as they are a smaller fish and she grabs them up no problem. All the feeders i introduce have been either bred in a smaller tank here in my house or purchased and quarantined for at least 10 days before i even think of feeding them to my Oscars. Its only when i give her bigger feeders that she kinda shys away from them and wont eat them. Any input on this topic is appreciated. Thank you again.