My mom has an 1,100 gallon pond, the filtration isnt all that good. It's your typical unit at Lowe's that has some bioballs and filters and a small uv sterilizer built in. It clogs up every 3-4 days and the pond is always dark. Has about 8-9 koi and some are very large and fat. Then we have the problem fish that are small black mollies (over 400 i bet)

We use tap water to topoff but dont use dechlorinator. What can I do to help make the pond clear??