I have a 3500gal pond in full sun. Over the course of my 15year pond experience I've learned that you need to have a good filter system. I built a Skippy (see online for instructions) and although a professional will tell you they are not good, it's been amazing what it has done for my pond. My pump is submerged and circulates the water once every hour. I don't think your pump if I remember correctly does that. Too slow and it gives the water time to gather crud but too fast and your filter doesn't have time to clean it out. I do use beneficial bacteria every couple of weeks and a product called Green Clean which helps with the algae. My water is fairly clear and you can see all the way to it's 4 ft bottom. I don't use a UV filter, just those two chemicals. I did remove all my plants because I live in a rural setting and I had a lot of problems with raccoons, deer, and critters getting in and hiding. I was afraid they were going to tear my rubber liner. I go out occassionally and check my pump and pads and if they have too much crud on them I simply hose them off. I try not to do it too much because I have snails that are helping with the water and I don't want to hurt them since they are doing such a great job. I had to learn to overlook the algae on my rocks and not want a perfectly algae free pond. I do not feed my fish at all and they survive on the algae and crud. I have babies every year so they must be happy. I also stopped draining and cleaning my pond every fall and let it overwinter and get some rest. I haven't cleaned it for 5 years. There is some crud on the bottom and I scoop a little of it out from time to time, but it just adds to the natural look. I have frogs, fish, snails, dragonflys, birds....you name it all naturally coming in. I don't have a lot of money to spend on it and have found that you can have a wonderful pond experience without breaking the bank as the professionals would have you think. I don't have koi for that reason. My fish are just goldfish, but they are going and doing fine. Good Luck