Hi, I have two red-eared sliders. I am not sure how old the are. I have them housed in a 40 gallon tank together, with large river rocks (not really huge, you know, just about an inch and a half large) and fake plants in one corner of the tank (they like to hide and chill out there sometimes). I have a homemade basking area with a ramp that they seem to have no difficulty using. I have the standard two-bulb lighting fixture, with a heating bulb and a UVB bulb
I have a water heater with a cover, and a thermometer on the side of the tank; the water temperature has stayed at between 75 and 78 degrees F. The air temperature near the basking spot has stayed around 85 degrees F. I have a water filter that has kept the water very clear. I feed my turtles separately, outside of the tank, hatchling pellets, though I have also begun to introduce dandelion leaves and other greens; they pick at them sometimes. I offer dried krill about once a month as a treat. Tersh is about one and a half inches long, and York is much smaller; they have also shown no signs of aggression towards each other; no claw fluttering, stacking, biting, or anything, and I observe them in the tank regularly.
York's shell seems to be normal, but I am concerned about Tersh. I will attach pictures below of both turtles. I'm not sure if Tersh is healthy, based on the appearance of his shell, top and bottom.