My 3000 gallon pond is about 12 years old, I have a 100 gallon skippy filter with half floor polishing pads and the other half with small and large bio-balls. It is fed by a 7200gph pump also going thru a 1200 Haywood pool filter that I used once a month to polich the water. This will take out smaller debri. I also have a large water fall fed by a separate 3200gph pump. I do weekly water change about 20% after I add bacteria. We started with 2 kols and now have 14 plus about 6 small fry about the size of a grain of salt. Was cleaning the bottom of some small pea pebbles and saw them in my net. I also have water lettuce which grow very fast and several small plants that were given to me, don't know thier name. My 4 water lilies finally died this year they only grew so much even though I fed them the tab and repotted them in larger pots. The Lilly's are the only thins that I have issues with thru the years, will address this in another thread. So I got 4 new tubers let see what happens. Never had a fish die on me for all these years. I am very happy with my pond water it's very clear. I read that you should check the quality of the water and so I was wondering what kind is test kits are the easiest to use?