i just bought a couple of fresh water fiddler crabs and put them in a ten gallon tank. The people at pets mart told me to get an undergravel filter to use in the tank.

I set everything up and the water is getting really murkey for just two crabs, and the undergravel filter is causing the water to bubble up on the top, almost like soap. I put in some "start right" that cleans out the chlorine, and a little bit of aquarium salt. What can i do to get the bubbles to go away and clean up the murk?

any suggestions would be great. thanx