Floating plants will shade the aquarium, reduce light for algae.
Algae grows where there is water, light, and nutrients. I have had terrible algae issues but have it controlled with these steps:
1. I have live plants, as they compete with algae for nutrients
2. Nerite snails love algae, I keep stocked up
3. I don't reduce the length of light, but give my aquarium a two hour "nap" (6 hours on, 2 hours off, 6 hours on). The theory is that plants do fine even if they get their light in blocks, but algae doesn't do well if you interrupt that 12 hour day.
It works for me.
FYI: that growth looks like fungus. Shrimp love it.