If you have fish or invertebrates or even live plants in the tank, don't add chemicals like hydrogen peroxide. I know some do, but that does not mean it is safe.
Algae is natural and will occur in any healthy balanced aquarium. The aim is to keep it under control, and with problem algae this can mean allowing some but controlling any increase. This is the usual approach in planted tanks because the algae can smother and kill plant leaves. In the absence of live plants, there is actually a benefit to algae, but an excess usually means something is wrong.
More info on the situation might help us suggest whatever.