Prevent algae growth

[GpsFrontier]

It looks like all you would need to do is fill the baskets with more grow rock. You want the water level to be about 2 inches below the top of the growing media. That way the top of the growing medium is dry, but the main root ball can still get plenty of moisture.

P.S.
I'm assuming this is a flood and drain system and not a NFT system.