Posted: Sat Apr 20, 2013 2:44 am Re: How much water should I have in my tank for 2 RES?
You can only put in what the tank will hold. If there is a cut out for the filter, odds are it is one of those "special" turtle tanks they sell.
So...if it were me, I'd fill it as high as I could (just below the cutout) and put the basking spot along or above the water line (making sure they have a way to reach it).
If they have a ramp that allows them to easily climb to the top, then it doesn't matter if it is half full or 10 feet deep. You just need to make sure they can get up to their basking area AND have a "high spot" for sleeping (something they can perch on that allows them to just stick their noses out for air when they sleep).
You may find better answers and get more advice on the "Indoor Habitat" forum; they are quiet creative.
"I know up on the top you are seeing great sights, but down at the bottom we, too, should have rights"
~ "Yertle the Turtle and Other Stories" by Dr. Seuss ~