Hi there,

Did you see this at the Seachem website?

"To target a specific phosphate increase, dose according to the following formula: 0.8vp=m, where v= volume of tank in gallons*, p=desired phosphate increase and m=volume of product to use in mL. For example to raise 20 gallons* to 0.1 mg/L phosphate you would use: 0.8*20*0.1=1.6 mL."

If you compare this with fertfriend your calculations should match up. I remember doing this a while back and the ppms matched up.

Cheers