Fiddler colony?

you can defiantly put some fish in the tank if you have a heater and make a spot for the crabs to come up and get air, but i would suggest tetras or maybe some ghost shrimp tiny fishes (1" max 2") that can get away from your crabs claw.- good luck!

So ghost shrimp are safe with crabs? I thought they might become dinner... Good to know they can be kept together- I've been considering a brackish tank.

You suggested Tetra- a rather broard group... which Tetra are salt-tolerant enough to go in a brackish tank?

actually i didnt realize i was in the brackish section when i asnwered this, but in this case im not sure if ghost shrimp would be dinner or not im guessing if you put at least 6 in 4-3 will survive, also instead of tetras i would really suggest bumblebee gobies they are wonderfull to watch and in brackish invierments they look beuitiful. also put some live sand in to make them a little bit more happy and at home. i get white clouds to feed to my eel my puffer doesnt like them but they are in brackish conditions. the white clouds become way more colorful when put into brackish they seem to not mind the salt. also The Purple Emperor Tetra does do well in brackish i heard, but i think other tetras arent compatible with brackish- they might live for a couple of weeks though, actually i accedently got an extra fish when i got my blue ram awhile the extra fish was a neon tetra so i wasnt sure what to do with him so i thought i just put him in my bracksih tank for my eel to eat but he lived for about 4 days until he got him, and i didnt see any signs of the tetra looking like it was going to die.

- good luck with your new community's!

You know, the OP never asked for fish suggestions, he just asked if he could keep more than one species (I'm assuming) of fiddler crab together.

[edited] by the way i had wrote something fairly offensive but i had to delete it because i want to stay on this site. and plus i was the first one to respond to his question, and it has been at least a day before anyone wrote to this so if your so smart and know everything i would have suggested for you to answer this first

and by the way i was giving suggestions to Wycco.

What is your problem?

I've never heard of a tetra that would live out its normal lifespan in brackish conditions. Most, if not all, come from low TDS waters which is the opposite of brackish.

Sorry if this is even more offtopic...

I'm sure you can keep more than one different species, if this even matters anymore. All are about the same size so the only risk I see is interbreeding.