Setting up an aquatic turtle tank can actually be a pretty big project. A lot of aquatic turtles, as they get older, become quite large and outgrow your standard glass fish tank. So glass fish tanks are appropriate for these smaller hatchling size aquatic turtles. Basically, your goal with setting up the depth of the water is to provide the turtle with room and depth to swim and submerge itself completely, to just be comfortable, to be able to turn around in the enclosure, and get some exercise.
When you're dealing with an aquatic turtle setup, we also have to think about the water quality. Aquatic turtles can be very messy eaters. They can also produce a lot of waste, so it is important to have some sort of system in place for keeping the water clean. A lot of times if the water looks clear to you, there still could be bad bacteria or different types of chemicals building up in the water that could harm your turtle. Most of the time, people use filter systems. These are the same sort of filtration systems that you could use with your fish tanks.
Again, because turtles are messier, you may need a more heavy duty type of filter to deal with their waste. Even when you do use a filter, you're still going to have to change the water. Partial water changes, at least, twice a month are recommended. Again, the more water you have in the tank, the easier it is to keep clean.
All aquatic turtles also need an area to come out on the land. This is called a basking area. They need to be able to get completely out of the water, dry out of it, and warm themselves up under a light source. While they're basking and warming up, they should also be exposed to an ultraviolet light source. The most common ways of providing heat and light in these aquatic turtle setups would be with actual bulbs that screw into hoods that either clip on or hang over the top of the turtle tank.
Some people will actually provide a land section of the tank that contains a substrate, such as bark. This is fine. Just make sure you're able to keep things clean. If there's a lot of moisture building up, you can actually get some molds and things going on with a substrate.
The other thing is to always look up, when you're setting up your aquatic system, the natural environment of the species that you have. Again, when we have a turtle as a pet, you need to do your research beforehand and figure out what that turtle's natural environment is like and try and replicate that in your tank. A lot of these turtles need a water heater, so that the water is maintained between 75 and 80 degrees. The basking temperature that they prefer is often around 85 to 95 degrees.
So, those are some things to think about when you're setting up an aquatic turtle tank.