[Krispyplants]

What kind of light do you have? What kind of co2 are you dosing and are you injecting pressurized co2? Have you been keeping up with your water changes before that 10%? What size is your tank? What kind of filter do you have? Have you been cleaning your filter? Have you been removing plant and fish waste along with your water changes. How long has your tank been set up? That does look like slime algae. Blue/green algae.

Bump: If that is slime algae, stop dosing anything with phosphates and try to feed frozen foods only. A lot of freeze dried, pallets and flakes has been treated with phosphates to preserve it longer.

 

[Krispyplants]

It's probably not an overfeeding problem. All I'm saying is that flake foods contains phosphates and can contribute to more algae. You may be dosing too much phosphates within your fertz. Too much water changing can be a problem too when phosphate and silicate can both be found in treated water. Some water source has less phosphates than others. You may have everything right for months or maybe even years but once you unbalance something, everything is adding in. What kind of fertilizers are you using? If you are dosing anything with phosphates, I advise you to stop because slime algae is a very good indicator of phosphate over dosing especially when you change water weekly.