Check My Math - Phosphate-E Dosing

[bzb]

@FutureInterest dropped off a bottle of Phosphate-E for me to try out. I did a 20gal water change yesterday and it didn't make a dent in my 0.12ppm phosphate reading (phosphate spike has been going on for about 3 weeks). I've reduced feeding, added a couple turbo snails and a sea hare, and the algae is still growing at a rate that worries me.

Current level = 0.12ppm / 70gal, goal of 0.05ppm

Bottle Instructions: 5mL per 20 gallons = eliminate 1ppm

17.5 mL = reduction of 1ppm in my tank
0.07 x 17.5 = 1.225mL = reduction of 0.07ppm

I'm not a fan of doing rapid changes, so I'm a bit hesitant to dose this, at all. But it looks like dosing ~1mL should get me to my target. I'm thinking I just do 0.5mL and check levels over the next couple days. Thoughts?

 

[ichthyoid]

A quick review and I agree.

70 gal is 3.5 x’s the dose per volume of 20 gal., so that gives the 17.5
5 x 3.5=17.5

The 0.07 is the difference between the 0.12 (actual) and 0.05 (target)
0.12 - 0.05 = 0.07

Slow is good!

 

[bzb]

How fast should this stuff work? I stopped feeding the fish on Monday, dosed 0.5mL of Phosphate-E and started skimming wetter.

Phosphates after two days = 0.11ppm

 

[ichthyoid]

Wow, I would have expected somewhere around a 20% decrease. Assuming the dosage/response scales linearly.

 

[bzb]

Well, I'm about to feed my poor hungry fatties, so prob have another spike