Also I see blinds in the background of the tank, are you giving your tank a lot of natural sunlight? The top of the vals could be getting a lot of light as they grow tall toward the light source. Adding natural sunlight can also increase light levels to exacerbate an algae farm. Either or, you might need CO2 to fend off the algae. Liquid carbon, like excel or glut, which is used sometimes in lieu of CO2, can melt vals and ancharis (elodea). However, I've read some reports that you can slowly and incrementally acclimate the two plant species to excel with lite dosing and gradually increasing -- but also staying consistent. IMO, using a liquid carbon is okay, while CO2 (or CO2 + liquid carbon) is best.