Help with dosing and water change routine
We have been battling BGA for a couple of years now. Since finding this forum things have improved but I am not sure where to go now.
I have just completed a BGA blitz. I have carried out 2 x 200L water changes back to back, have cleaned the cannisters, added NO3, done a black-out for 3 days AND treated with erythromycin. Done another 200L water change, turned C02 back on, added more KNO3 and installed new tubes.
Now have 300w of light over a 180 US g tank, pH 6.8 (co2 20ppm) KH 5, GH 5 NO3 20ppm, PO4 2ppm
I uncovered the tank to find all the BGA gone and I want to keep it that way!!
We usually carry out 1x 30% water change per week and add all ferts after the change. I tried to reduce the amount of ferts by 1/3rd of reccomended amount to stop increase in concentraion but KH and GH seem to be creeping up over time. NO3 always seems to be low when I check.
Is there a way to use the Estimated Dosing Index and carry out only 30% water changes or do I have to do 50%? I can't do anymore than 30% at a time and find it difficult to fit in 2x water changes a week.