He was actually only able to get that far because it was locked. When I adopted him, he came with a tank, a cracked tank but a 40 gallon tank nonetheless. I decided to keep it despite the crack, but as I examine the top more, the left side doesn't slide ALL the way in. It's the tiniest space, he's been working on it diligently since he got part of the way out but hasn't been able to get more than his tongue out since.

I'll probably end up getting a new tank as his christmas present after that scare.