Filtration
Filtration is the most important thing of them all. It provides a clean healthy environment for your turtles, and lessons the work for you. Turtles require 3x the filrtation power than fish do. Ex. 20 gal. tank requires 20 gal.
filters for fish, but for turtles you would need filters on it for a 40-80 gal. tank. Turtles need a very clean environment, because they are easiley able to get diseases on their shells do to dirty water. There are 3 different types of filtration, and 2 types of filters. Mechanical, Chemical, and Biological are the 3 type of filtration. Top water and undergravel are the 2 types of filters you can get. All 5 of these filtrational devices are required for turtles. You should have a good top water filter that does at least the 2 types of filtration. And an undergravel filter that fits your aquarium, with powerheads. Most top water filters take care of the mechanical, and chemical fitration, but undergravel filters do the biological part for you and keep your gravel looking nice. Also I would recommend snails to help keep your aquarium looking clean. You should also clean your tank once a week with a gravel vacume only taking 25-35% of your water out. And once every other month completely clean it. Recommended filter companies:fluval, marineland, emperror, penguin, and regent.