20 Gal Rapid Green Hair, Black Beard And Dust Algae Growth Help

I’ve made a post about this tank before, I now have parameters to add to make the cause easier to target.
Nitrite: 0ppm
Nitrate: 0ppm
Ammonia: 0ppm
pH: 8-8.2
Temp: between 78-80
Dosed with Flourish Excel daily
Lights are full spectrum, 11 hours a day
Weekly 25% water changes
Algae is wiped off sides every 1-2 days
Filter is clogged with brown sludge and has to be cleared out every 2-3 days, most plants get coated in algae and start loosing leaves.

I will be adding some pH down and finding a way to maybe break up the light cycle to two 5-6 hour shifts? Below I linked some pictures of the algae and tank.

 

 

So I immediately see multiple reasons you may have issues with algae.

First, how planted is this tank? With readings like 0,0,0 you would have to have a pretty heavily planted tank to show 0 nitrates in a fully cycled tank.
Dosing Flourish Excel daily seems like a lot to me. I have three pretty planted tanks, and I only dose Excel every week. Once a day seems like a lot, though I'm no Flourish Excel expert.
Lights on for 11 hours a day is a main source of your issue, as that much light is exactly what algae thrives in. I would really turn that time down to 6-8 hours a day. Probably less for a while to starve the algae.
I would not add pH down as that stuff is honestly garbage. Your pH is perfectly fine and adding that product has been known to cause huge pH swings which can definitely kill your fish.

 

I previously only dosed co2 a couple times a week and wondered if the light to co2 ratio was off. But I could definitely see the length of the light cycle being an issue too. I will try scaling it down to 10 hours at first to ensure the plants will be fine. I do have a whooooole bunch of plants in there and the algae I believe also feeds on the same stuff so it’s safe to say I have a pretty large water cleaning crew, haha.

 

I would really cut back on the light. I think it's really the main issue you're having with that algae. The algae will starve while the plants should be fine. I would do 8 hours. The longer the Algae sits on plants, the sooner it'll put dead spots on those plants or kill them.
I know that feeling with the Nitrates. In my Betta tank I rarely see Nitrates. It's pretty heavily planted and crystal clear, but I also have zero algae in that tank.

 

Okay I’ll try really bringing the lights down, my bettas usually get around 8-9 hours and that keeps things clean.