Hey all I'm new to post here on the site but ive been visiting regularly and really enjoy the site so i decided to join, i have a question about one of my 5 RES if anyone can offer some help it would be GREATLY appreciated.
I have have 5 RES i keep them in a 55gallon aquarium with 2 different lamps, a huge water filter and a good heater so i know the temps and the water clarity are good. all of them are extremely active eat and everything. but one of my hatchlings recently has developed a black patch (for lack of a better term) on its shell, and he now swims almost on his side.... it makes very little sense to me and ive never seen this type of thinng before, would anyone be able to tell me what they think it is? also would it threaten my other sliders?

