Alge in roots

The roots are not rotting but there is green alge in some of them outside the containers in an ebb and flow system with the light now blocked from them. All other specs are in the norm. It was posted somewhere about a product other than H2O2 that "eats" alge and helps the plants feel happier but can't be found at this time. Can someone recall what this product is and post it. Thank you.
 
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