Guppies, A dozen or so every two-three day's.. When you get them over 5-6 inches then go Talapia,Smelt,Massivore,Shrimp,Scallops,ect.... I've grown well over 10 out with great luck!
when 3"-6" i fed bloodworm and smashed prawns, and then moved onto hikari massivore and mussels and squid and fish fillets and pretty much anything it would eat.
I am having a problem getting my 5in TIG to eat also. I have tried shrimp, small minnows with no luck, I guess earth worms will be next. By the way how fast do TIG's grow in comparaions to say tiger shovel nose or red tails??
Grew my 2 on from 2-3" on tiny feeders, they wont refuse them.
Once 4" plus wean onto pellets and whatever else their eat, but dont feed much-every few days is fine. never had problems with mine and grew fine. Here's a pick taken months ago