I need to make a self cleaning/sustaining turtle tank w/ fish?

sorry but that’s not posible. It’s possible that he didn’t have algea in the tank due to live plants and algea eating snails and fish, but you would still need to do weekly water changes to keep the nitrates and other nasties in the water to sutible amounts. seualy fish and turtles don’t mix, as the turtles will sooner or later eat the fish.

You don’t have to clean it nearly as often if you use the guidelines below.

“RES’s enjoy large areas where they are free to swim. These turtles also require a basking area, where they can leave the water and enjoy the light you provide for them. UVB heat lamps are usually the best option and most common among those taking proper care of their turtles. However, UVB heat lamps have not been proven to have the same quality as direct, unfiltered UV rays from the sun. Therefore, it is recommended that on days with more sun you take your turtles out with you to enjoy it, even if this is only possible in the Spring/Summer. Note: Although not nearly ideal, RESs have been known to remain healthy even with a regular light bulb or halogen light as their source of basking heat

-For the basking area, the best choice is an actual dirt or sand area, if this is at all possible. This is especially suggested if you have different sex turtles. The real land area will allow for an impregnated female to lay her eggs, or at least attempt to.

-Plant life, either fake or real also increases RES quality of life, mimicking their natural environment. The real plants can also serve as a source of food.

-Turtles highly enjoy fresh, clean and clear water. A good filter can help accomplish this. Also, once every two weeks about 25% of the water should be removed and replaced with new water, and the filter cleaned. It is also strongly recommended that if you have a large enough tank, as well as the proper pH and water temperature, to keep fast freshwater fish. In a large enough tank with areas for fish to hide, it is very unlikely that they will be eaten. Meanwhile, the majority of freshwater fish will feed on the leftovers of what you feed your turtles, as well as the turtle’s feces, both which allow for a much cleaner environment for both the turtles and the fish.”