Tank Size

Turtles need certain conditions to thrive. If they don't have those conditions, they will be stunted and will essentially be surviving not thriving. Turtles require 10 gal per inch of shell for tank size.

(footprint space is more important than depth/height)

Turtles need room to swim and to be able to run completely around in the area. They also need exercise and enrichment. With small tanks, they can become deformed.

Turtles also urinate and move their bowels in the water that they eat in and live in. Filters can only do so much. If there is a bigger tank, there is usually more water which keeps the waste less concentrated.

The smaller the tank, the higher the chances of it overheating. This will cause the water as well as the overall ambient heat to increase dramatically.

Babies should have 1.5-2x the shell length in depth as their lungs are not as developed and tire quickly. Adding resting spots does not give them oxygen to breath, so that is not a solution.