I had two Fiddler Crabs in my 20 gallon that were originally for the 25gal tank but Meclizine and I were afraid of them eating the shrimp. All our tanks are planted. Since putting them in the 20gal I'd been noticing that my dwarf hair grass looked like it was getting eaten my either the fish or snails. Also that some areas were the patches that I planned were gone. Well, one day this pass week when I came home from work in the morning I also inspect all tanks to make sure all is well. All is well and when I turned the 20's lights on I found the female Fiddler eating the DHG. I also saw the Male eating some Java Moss that I tied down on drift wood to grow. I had to put both of them to the 10 gallon tank with Dragon (my betta) and they are eating those plants to but I don't really care much because it's the quarantine tank. LOL. Didn't know my crabs were vegetarians.