My opinion of test kits isn't much. You get what you pay for which was proven to me once at a county testing lab. I was also advised not to buy one by a pond store that sells the kits. When people test their water they feel they have to do something to correct their high test results. So they go out and buy more stuff to put in their pond based on what they have read somewhere on the internet. They can't see any difference, in other words, their fish are still alive or whatever else they were trying to fix seems to have worked so now they spread the word on the internet that product X does the trick, When in reality the pond probably took care of itself or whatever they thought was the problem really wasn't a problem. Think of a ditch along the side of the road and think of the frogs and other things that live in that environment. Test that water and see what you find, just don't tell the frogs they are suppose to be dead or that the water isn't supposed to be clear. Although clear water doesn't mean healthy water it's what everyone is after.