So he will go to strike at it but then end up not? He defiantly seems interested then. How often are you feeding him? Typically you don't want to feed them more then once every 7 - 10 days. If you are waiting that amount of time and he still won't take then perhaps try and drop feed him instead. Just kinda make it dance around a bit to get him to notice that it's there then set it down in the tank and see if he'll go for it that way.

Also I was just a little confused about how you worded your whole heating situation. Is it you have a lamp or something on one side and a heat mat on the other or just a heat mat on one side?