sealant

(I'm in the UK) So I'm hoping that, in the next couple of weeks, I'll be the proud owner of a Hermann's hatchling, and naturally I've been building a vivarium for it to spend the first few years of life in before graduating to a full table. Said Viv is your average 4x2x2 made of MDF with a...

I'm trying to seal a terracotta dish so that it doesn't suck moisture from his food. Is there a safe sealant that i can use that won't be toxic to him or leak anything into his food?