Green water worries

I’m using the wick system in my garden from your book Easy Marijuana Gardening. The water in the reservoir turned green after a few weeks. I drained it, cleaned the reservoir with hydrogen peroxide, and refilled it. It has turned green again and so have the wicks.
I’m thinking algicide is probably a bad idea. Would a lid over the reservoir do any good? I’ll need a big lid and not be able to find one. Hopefully the green water is okay? Do you have any suggestions?

Rayz Hell,
Romulus, Michigan

A lid over the water would be a great idea. Green algae requires light for photosynthesis. Cutting off the light eliminates them. The tank can be covered with a sheet of black plastic or cardboard.

You can also add 3% hydrogen peroxide (H2O2) at the rate of about an ounce per gallon daily. The hydrogen peroxide kills water organisms such as algae and stimulates the roots by adding oxygen to the water mix.

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