Help! My red eared slider was eating at his basking dock and now he is not eating. Is there anything I can do?

I bought a new tank and basking dock for our 1 1/2 year old Red Eared Slider. When we put him in the tank with some new decorations he started biting at everything.Then he started biting off bits of the basking dock, that we found out was foam. Last night and today he wouldn't eat, even his favorites. I called the company that the dock came from, and they told me that he could be doing it because he needs minerals and/or needs to trim his beak. But the foam could cause a blockage. If he has a blockage is there anything I can do or give him, before I take him to the vet? As with everyone money is very tight. How long can he go without eating his normal food? Please help us! We don't want to loose him!