First be sure you clean the tank of algae, manually, do water changes 50-60 % each week
Then be sure you add more co2, try to reach 30-35 ppm and have good flow so co2 is reaching each corner of the tank
After this aff more fertileser , try to reach 15 ppm NO3 , 1 ppm PO4 , 0.2 ppm Fe
Most...