Crabs?

[Jakaris]

This is a twofold question, really: I have a 5 gallon tank that has 4 guppies in it, and I was wondering if I could possibly convert it to brackish and add some sort of crab (with the ability to get to the surface).
I've heard that guppies, along with mollies (I know its true for mollies) can be weaned from completely freshwater to brackish to saltwater. However, I've never done that, and would like to know if its possible. Also, would the crab just kill the guppies? And what other options might I have for that particular 5 gallon tank, if I were to, say, put my guppies in my large tank.
Thanks!

[squirt_12]

the only crab that i know of is the fiddler crab but it will eat any other living animal (besides other fiddlers) that are in the tank with it. Unless you have enough water so that the fiddlers can't reach them. But don't forget that the fiddler needs alot of land. And i think that a 5g would house 1 fiddler. and i doubt that once you get your substrate in there and have land that you would have any room for any fish. Cause fiddlers like sand so you would have to get some sand(gravel will work but they like to burrow in sand) and also to go to their land you have to slope the substrate so that they can walk up it easily.

I hope this helps.