What Bunny13 said. Its my little Dr. Zoidberg she's talking about.
Check him out:
Dr. Zoidberg
He lives peacefully with Goldie:
Goldie
These guys live great together. As long as Zoidberg is well fed, he doesnt so much as look at Goldie. I keep him well fed by feeding him daily, as well as keeping some ghost shrimp in the tank for snacks/to eat the algae. Turns out Goldie eats them more than he does. In fact, I dont think he's ever tried to eat one of them Today Goldie snatched a shrimp pellet right out of his claw, and he all he did was go looking for another one. They're curious, and Zoidberg likes to crawl around a lot. I can see that his curiosity might lead to an untimely demise if he could crawl out of the tank, but I dont think that is possible. If he really tried, he could climb up the filter thing, but he's content as long as I rearrange the tank a little each day. He spends his time moving the gravel, piece by piece, to exactly where he wants it.
He has been underwater for months now and has not drowned. I wouldnt worry about it. Unless he's sneaking out at night and somehow climing back in, he hasnt had a breath of fresh air yet.
He's a funny little pet. If you want any more info, feel free to ask.