Algae needs at least 2 things, nutrients (however small that may be) and light. If you can cut the light down it should help control the algae to start with. I would recommend dealing with the head of your problem first rather than put band aids on something. If light getting through your container? Is it a clear plastic or light plastic container? Maybe consider painting it or wrapping it with something. This would probably help you out much better than hydrogen peroxide.

Algae is ubiquitous in hydro whether you use hydrogen peroxide or not.

Make all the stuff that handles nutrient opaque....this is the best you can do.

I am using white styrofoam for the raft and it is not a perfect fit. So some lite gets in around the edges. Maybe i will put some foil around the edges to seal out the light.

I am using about 6gallons in each tub so i am going to prep some new nutrients in spare tubs and swap them out. Maybe i can get a fresh start and keep ahead of the algae.

Thanks!