Well then you have a low NO3 tank which is why you got this and cannot get rid of it.
Adding plants, and all the ferts other than NO3 will drive the NO3 to zero, then the BGA will take over and you cannot stop it for long.
So, clean off all you can now, start adding KNO3, then stop adding Seachem Potassium(the K+ is potassium in the KNO3).
You will also need some PO4 as well.
Order some KNO3/KH2PO4 from
www.Gregwatson.com
2-3 lbs of KNO3 and 1 of KH2PO4.
Should last a decade or so.
Dose 1/4 teaspoon KNO3 2x a week. Dose the KH2PO4 2x a week as well, 1/16" teaspoon(divide 1/4, 4x).
Add about 5mls of flourish 2-3x a week.
Seal up any air vents or lips on the trickle fiter dry section with duct tape etc, raise the over flow box level so the water only falls about 2".
Add CO2 into the intake of the return pump from the sump.
You can kill BGA easy with a 3 day black out(plants are fine, they are shipped often times longer in total darkness). But.....you should just clean the tank up real good, do about 60-70% water change and then add the
KNO3(add 1/2 teaspoon this time) etc and see. You might not need anti biotics or a black out etc, note, blackouts are free and take the same time to work as antibiotics.
Do weekly 40-50% water changes and dose the KNO3 routinely.
Plants should perk up
Regards,
Tom Barr