Do fiddler crabs fight?

Should i add fish tank freshwater salt to my community fish tank, and question on fiddler crabs?

• Its a 55 gallon community tank contains the following.. mollies, guppies, platies, kuuhli loaches, dwarf frogs, cory cats, and a very small common pleco. i have a whole bunch that i bought cheap at walmart and i read the back said it helps the fishes lungs and stuff... so should i add it? Ok now onto the fiddler crabs... If i add one of those attachable turtle land thingys,(maybe cover it in some moss or something) can i have fiddler crabs? and maybe add some really tall fish tank plants that stick above the water a little for them to go on.. or can i not have them in a community tank with those fish.. and ik u need to have brakish water for crabs.. thats why i want to know if i should add the freshwater salt. thanks need to know asap!

• Answer:

  First lets distinguish which types of salt you would use for which situation. If you want to mix water and salt to make a brackish water setting or a saltwater setting then you need to buy a Marine salt mix. This will increase the specific gravity of the water and make a suitable environment for a fiddler crab. This marine salt mix shouldn't be used in the presence of freshwater fish. Regular Aquarium salt should not be used for this. It doesn't contain the same properties or elements and will not be suitable to raise the specific gravity. Regular aquarium salt can be used in a freshwater tank as a defense against minor infections and defeating things like Ich. I would not, however, use it habitually or all the time. The dwarf frogs, cats, pleco, or any other scaleless fish would eventually become irritated by the salt and could stress them out. So, as far as the fiddler crab goes, I wouldn't put him into the 55g. It would really be difficult to make a suitable home for him because the tank is soo tall. I'd look at a smaller tank -10g or so with a small internal filter. Fill the tank up half way with water and mix a marine salt mix to get salinity to a proper level (1.005 - 1.010). Pile up some gravel or sand on one side so he can get out of the water if he chooses. :) Good luck, I know I've lost several fiddler crabs to similar situations. Mine never survived long in freshwater communities. PS - they are escape artists. I found one of them on the carpet in the next room away from the tank! That's why I suggested an internal filter for them so they can't climb out. :)