We have a "fountain" which looks like a cascade of rocks, stepped down in 4 layers. It laid nicely along a slope near our east deck, and we ran a cord out there, plugged it in and we have a lovely sound of water.

BUT, in 4 months, the algae has covered each layer. At the bottom of the rocks is a "pan" filled with small rocks, which is where the water returns, to be pumped up and out again.

If I put bleach in there to kill the algae, I am afraid I will kill numerous snails and things that not only live in that pan (those I could pick out) but other small creatures. AND we have some beautiful red wasps that come to drink from it every afternoon.

How could I kill the algae without damaging the wildlife?