Great looking set up. If the lights give uneven light distribution, you can try mounting them in the short ends of the tank. I’m afraid you’ll get a ton of light spill.
It’s Rapunzel’s hair algae. Recommend doing during a water change and siphon it out while you scrub. I insert a rigid pipe into your siphon hose and tape/rubber band a brush to the end so it’ll suck away the algae while you scrub.