Green water with no plants or fish

by Nancy
(Maryland, US)

My pond recently was drained for some repair work. The entire thing was cleaned before refilling and looked great. Because of the shallow depth, we have neither plants nor fish (the many birds of prey and raccoons also make fish a bad idea). Unfortunately while we were away for 2 weeks the circuit breaker for the pond tripped and the pump was off for the 2 hottest weeks of the summer. My clean pond now has green water again, though the surface water seems cleaner. We have lots of water movement as the pond drowns out the noise of a highway. The rocks on the bottom making cleaning the whole thing again an unenviable task. Any ideas?

Doug says - you don't have plants to act as biofilters to balance the pond chemistry and you run a high-volume pump to combat traffic noise. Bottom line - you've create an unbalanced ecosystem and the only result of this will be algae growth.

If you can't balance your system with the use of plants - and you want clean water, the bottom line is you're going to have to install some form of uv-lighting or chemical sterilization to stop and kill algae.

No amount of pond cleaning is going to remove the basic problem in the system. In other words, you can clean all you like and as soon as you stop cleaning, algae is going to return. In a normally balanced system, there will be a bloom and a return to clear water. In an unbalanced system, there will be an ongoing bloom, bit of a crash and bloom with consistently green and dirtly water.

Algae is a result of imbalances in a system - and you either cure those imbalances or you create a mechanical solution.