That's a good start... they can get through it though.
My g/f had sixline that used to cram himself into a small hole in the rock anytime he got stressed.
When we moved her tank from school to her house, I couldn't find the sucker anywhere, so I assumed he jumped.
A few hours later when I was adding rock back to the tank, he popped out of one of the rocks and was swimming around like nothing happened :lol: