Trans Instruments has specially designed the KoiMedic tester to measure the delicate salt concentration in the pond. Two models of your choice measuring in percentage(%) or parts-per-thousand (ppt). The testers are accurate and easy to use. All you need to do is turn it on and dip into the pond water.
Summer usually means increased pond water loss due to evaporation, which of course leads to topping off our ponds more. You should always add dechlorinator when topping off the water level of a pond. Any amount of chlorine (such as that found in treated water) can be harmful to your fish. Even if it is not enough chlorine to mean immediate death of the fish, this chlorine can still cause harm to proper gill function.