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Auto-Fill (The Good, The Bad, and the Ugly)

The Good
Auto-fill devices have become more and more common in water garden installations. The idea of keeping the pond full at all times is great. An auto-fill is hooked up to a water source so that when the pond's water level drops due to evaporation. A float is installed at the level of the water surface, as the float drops with the water a valve is opened allowing new water to enter the pond.

The Bad
Most auto-fill float valves do not remove chlorine from the water. Small amounts of chlorine will dissipate on its own before harming fish. Any amount of chlorine can harm the gills of your fish, prolonged exposure or exposure in high doses can kill the fish. If using a float valve, you may wish to add a little dechlorinator on a regular basis to help neutralize the tap water additives. There are kits like the PondFil Float that use a cartridge filter that removes chlorine from the water prior to entering the pond.

The Ugly
A leak in the pond may go undetected using an auto-fill. When a leak occurs you will be adding larger amounts of new tap water and larger amounts of chlorine, eventually leading to gill failure in the fish and ultimately death.

Even Uglier
Mechanical parts don't last forever. When the float valve fails this could mean a constant flow of tap water entering the pond.

Bottom line
Auto-fill float valves can save you the trouble of dragging a hose to your pond when evaporation drops the water level. This can be a big help, but if using this type of device it is good to have a little knowledge of the benefits and risks and to monitor the fish and the valve regularly.