Water does evaporate in hot weather and topping off the pond about once a month is normal. Add dechlorinator to any water from the tap. Chlorine burns the gills of the fish and will kill them. As we pointed out in the paragraph above, having any readings on either test can and often kills fish. We're here to help you.
Ponds are as unique as snowflakes.
You may have an outside filter and pump or they may be submerged. You may have 100 gallons or you may have 1000. Do your homework and know as much about the pond as you can when you visit. Read the labels on the pump and filters. Know the fish load and look over the fish for signs of distress.