CichlidFish.com - Fish That Think.

I have an 8 inch frontosa in a 40 breeder with a mix of other smaller africans mostly from tanganyika and he hasn't eaten anything but possibly a few ghost shrimp since I bought him over two weeks ago. I've tried feeding him cichlid veggie flake, prawn, formula 1, cichlid floating pellets, large sinking pellets, spirulina discs, ghost shrimp, and last resort rosey reds. So far nothing has worked. He chased the ghost shrimps around a little but I think the other guys ended up getting them all in the end. He is so beautiful and I'm at my wits end , worried sick. The temperature is 83 degrees and the ph is 8.3 or 8.4. Maybe he was in a bigger tank and is refusin g to eat in my 40 breeder, i dunno. But I really need some help. How long can he survive without food? Should I raise the temp? Take out the tankmates?