• You are viewing the forum as a Guest, please login (you can use your Facebook, Twitter, Google or Microsoft account to login) or register using this link: Log in or Sign Up
  • You can now follow UKAPS on Instagram.

Phosphate again!


6 Jul 2008
London, UK

I'm just about to mix my own EI but don’t understand something. Because this will be the first I'm going keep everything in separate bottles in the first few months to see what happens.
What I don't understand is the added amount of Phosphate. James and ceg advises the concentration should be around 3ppm/week. In the dosing table I’ve found this:

In 40-60 Gallons (152-227 litres) add 1/8 tsp KH2PO4 3x a week.
It's 0.375 tsp/week. By using James dosing calc the result I get is 9.6ppm for a 180L tank.
152L - 11.37ppm
227L - 7.61ppm.
That’s way over the recommended concentration. Please correct me if I’m wrong or missed something. I can’t really see the point of the 3x overdosing. But! I’ve seen on this forum a few days ago some1 accidentally put a tsp in the tank instead of 1/6th and the result was rapid growth. Does this mean the concentration should be even higher than the table says?

And also would like to ask can I mix the salts with de-ionized water? I have about 5 litres from Halfords, it's called "Battery top-up water". Found it in the shed and want to use it but not sure if it’s safe!
I've seen on James site he recommends Hydrochloric Acid for the trace element mix. Do I really need it? What is that for and where can I get some?
Planning to dose everything 6x a week instead of 3 (halving the amounts). I know myself I can get confused easily and don’t want to mix up the days! :) Can this cause any problems? Meaning the phosphor-iron relationship? Or it’s not an issue once they’re in the water?


3 Jul 2007
Bexley, Kent
Standard EI dosing adds approx 2ppm PO4 3x per week. ie 6ppm per week. Because the tables quoted are for a range of tank sizes you will always get some variation of amounts. This doesn't really matter that much as it's only an estimation that is designed to work with heavily planted high light systems. After you become comfortable with dosing you can normally reduce amounts to suit your own particular setup. You shouldn't really need to dose more than EI unless you have masses of fast growing plants and massive levels of light.

To mix the nutrients i now just use plain tapwater with no probs. No real need to use demin water but if you wish to use battery top up water then that'd work fine.

The chelators, especially EDTA, that are used are more stable at lower pH's which is why hydrochoric acid is added. Also seems to help prevent mold growing.

Daily dosing is great and as long as you let the PO4 solution mix in before adding the traces (or vica versa) then you won't have any probs.


Similar threads