red ear sliders, water wont stay clean

Question
I have two red eared sliders, one male and one female. They are both about a year and a half old, about 3 1/2 inches long.  I have them in a 30 gallon tank with about 15 gallons of water. I use a Cascade internal filter that is supposed to filter up to 20 gallons of water.  I can not seem to keep their water clean for more than two weeks. I changed the water and filter two weeks ago and the water is now green and murky. It's hard to change their entire tank every two weeks, I cannot lift the tank alone. I was wondering what I could do to keep their water cleaner for a longer period of time. They are constantly shedding so I don't know if maybe that is a factor in the dirty water. Thank you for your help!

Answer
Hi Courtney,

The filter that you have is a good one. Make sure you have filter carbon inside the filter chamber. Some other trick are feed them minnows. The pellets are notoriously known for making water filthy quick. Also put some very small snails and plecostamus fish in their tank. They will eat excess waste and scraps that the turtles leave behind.

Hope this helps,
Nate
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