Make sure to clean and sanitize that old tank before moving your little guy in there. Considering the former occupant passed away, it would be a safe bet to clean the tank. You have lots of options, the easiest of which would be to fill the tank with a 10% bleach OR ammonia solution and let it sit for 30 minutes (don't mix these two chemicals, noxious fumes will result). I recommend using ammonia, as its effective against coccidia.
Process is rather simple.
Step 1. Warm soapy water to clean and scrub any debris from the tank, then rinse
Step 2. Thoroughly wet tank with 10% sanitizer solution, and make sure it remains wet for at least 15-20 minutes. I recommend you fill the tank up at least 3" up from the bottom with the solution, then spray the rest of the sides down. Most of the pathogens will be concentrated where the substrate was, and that means the floor and a few inches up the sides. You might have to spray the rest of the tank several times during the 30 minute cycle, as it needs to remain wet.
Step 3. Rinse rinse rinse, and rinse again. Keep rinsing until you can't smell the solution. Since its a glass tank, spraying it with a hose should be easy enough.
Also, not to be a bother, but from the look of those pics your little guy is on colored calcium/vita sand. If that's the case, then switching to a standard sand would be a better alternative. Safer for your animal and cheaper for you. Loose substrates are often inadvertently consumed with food items, and this can lead to the substrate building up in the digestive tract, which can lead to something called impaction (clogged internals). Additionally, the dust from loose substrates can irritate eyes and lungs, and the dye used in many artificial sands will stain reptile skin after prolonged contact. Lastly, loose substrates provide a wonderful breeding ground for bacteria, which can be tracked back to you when you handle your animal. Natural sand is not as bad, as its less likely to pose an impaction risk (doesn't clump like calci-sand when wet), and will not stain your animals skin. I recommend ditching loose substrates completely, and using paper towels until your little one is older, then switching to stone tiles or one of the other solid substrate options. At the very least though, natural sand is better then the calcium stuff any day of the week.
Nice looking animal, and he looks happy! Good luck!