first off, nice looking wolf u got there. looks pretty healthy. ok now im gonna try and help you the best i can. it seems that sometimes people come on here and ask a question and they receive answers that they do not listen to or jus completely disregard. first off, its nothing but cruelty to keep that wolf in a 55g till it is 16in, that will do nothing but stunt its growth and cause other issues, so sweet talk ur mom into gettin that tank earlier. at this size he will be fine for a lil while in the 55g but try and get in something larger, for most wolves grow an half an inch to an inch a month until 12in then it slows down somewhat. now to the diet, all three things you listed are def. not a staple/healthy diet for this fish. salmon is oily and fatty, not really healthy for the fish, and it can mess up water parameters from what i have heard. beef is not easily digested by fish, wolf fish are piscavorous which means they eat other fish, not beef, gold fish are a coldwater fish and not tropical. they are fatty and of little nutrional value to wolves. this diet could cause your wolf to die much earlier than it could actually live. try and get the wolf on dead foods, go to the grocery store and buy raw fish filets like tilapia, catfish, and etc....cut it into pieces and toss it in. whatever u dont use freeze it, and re-thaw for later use. raw shrimp is also good. stay away from cooked stuff because its not as nutritious and could have other additives in it. if you want to feed some live items as treats use earthworms, tropical feeder fish like cons, guppies, or etc, crayfish, although at this size make sure its a crayfish he's actually able to tackle...lol. dont get one to big.....i hope this helps and you actually listen to this advice.....
oh yeah and from ur vid that tank looks bright and doesnt hv any cover for the wolf to hide and relax. they do not like bright light and love to lay in driftwood or plants or something. get some driftwood, or something like a cave or something, they feel much more comfortable with places to hide. they are a noctural fish so they will be most active at night. good luck