I have two RES, I believe both are female. I have had them for 8 years. Unfortunately I did not research about them beforehand and went with the poor advice of the store owner on how to set up their habitat when I purchased them as juveniles. One of the turtles has recently developed a shell problem, more on that later. In researching the shell problem I have learned that the habitat I have them in is way less than ideal and suitable. I am in the process of changing that.
The current tank is a 40G (36x18x18), and up until recently I had it set up about half full of water with a pile of flat rocks in one end for a basking area. I had a screen top with a heat light over the basking area and an 18" fluorescent tube fixture with the same bulb I was originally sold for the previous 8 years. It had a small submersible power filter with some foam for particle filtration, I would occasionally add some carbon media in the form of carbon impregnated foam material. I had a small submersible heater also. I would change most of the water at least every two weeks. I have a well with a whole house filtration/softener system that produces water that is suitable without further treatment. The turtles rarely got direct natural sunlight.
I realize 40G is way too small for even one RES let alone two, I am looking into a new tank as finances allow. I have built a ATBA (24x18x12) out of 1/2" acrylic that I got as scrap pieces from my work. I attached reptile mat to the basking space with zip ties. The basking space has a reptisun 5.0 CFL above it that is on for 12 hours daily and a heat light that is on for 2 hours intervals throughout that 12 hour period. I have cut the old screen top to fit over the other part of the tank and the old 18" tube fluorescent is over that part of the tank (see picture). I have ordered a new canister filter (API Rena Filstar XP Canister Filter-L) and media for it, it will be here on Friday. I need to buy a new tank heater. The tank is now full of water about 2 inches of space below the screen top/bottom of the basking area. Great news, one of the turtles, the one with the shell problem has already found the basking area and is using it regularly. I have also been taking the turtles outside every day that it is possible to expose them to natural sunlight.
Here is the problem with the shell (see pic). I think the problem is caused by the turtles own claws and due to the fact that the habitat was so inadequate. The turtle would constantly be swimming into the glass of the tank or into the rocks and I think repeated contact of the turtle claws with the area of the shell near where the legs tuck in caused the shell to wear. One side is much worse than the other and bleeds on occasion. The other turtle seems to be fine. The turtle with the shell problem is much more active than the other. Please let me know what you think. Am I on the right track? Is my diagnosis of the shell problem correct? The nearest listed herp vet is hours away. How else could/should I be treating this shell problem? Do I need UV light over the portion of the tank the part that is now covered by screen or is regular fluorescent OK? Does the screen block the UV/does the UV penetrate the water?