A good decent test kit is Aquarium Pharmaceuticals Master test kit. It's not the best kit but it's not the cheap strip one either, Good product for the money! It should have Ammonia, nitrite, nitrate, and PH. I also recommend getting a hardness test kit, strip isn't to bad on this as your really just wanting to make sure it stays high enough to keep the buffer up so the PH stays stable. Also a pond thermometer. It's really a good idea to get a test kit and know what your water is doing and why. Hint/Tip: 90% of all Goldfish and Koi illnesses are due to or related to water conditions or stress. Over feeding and declining water conditions are probably the top two killers of most pond fish. Predators are probably the next in line.