Henry Hatch

Guru Class Expert
Aug 31, 2006
Hello Tom,

After numerous failed attempts at growing plants, I discovered Estimative Index.
It works. My tank has been set up for about 3 months. I have traces of algae and very strong plant growth. I ran into a bump in the road recently with a mild case of blue green algae. I dosed the tank with erythromycin for 5 days and it looks like the stuff is gone. However, I want to be sure it does not come back now that I have completed the dosing regimen.

Since this stuff is actually a bacteria rather than a true algae, should I continue my
EI dosing regime ?

My tank is a 30 gallon very heavily planted tank with 60 watts of light and co2 levels normally above 30 . I have been dosing nitrates at 15 ppm, iron at .3, phosphates at 1.0 and potassium at 15ppm. I also dose with Flourish 8 ml. My GH and Kh are 4-5. I dose once/week.

I check N,P ,and Fe regularly with Laomotte tests.

Should I make any changes ?

Henry Hatch


Tom Barr

Staff member
Jan 23, 2005
Glad you have decent test kits.

Oner thing about EI, you'll need to dose 2x a week, not once, at the end of the week you should be bottoming out on the NO3/K.

PO4 limitation does slow NO3 uptake down and CO2 uptake as well, but the plants tend to do okay with low PO4.

But just divide the EI dosing into 2 or 3x a week routines, with about 30 ppm of NO3 as the target total for the week.

You likely have 2ppm a day removal, so this will maintain about 5-10 ppm and a max build up of about 30 ppm for this tank given the comments you have made thus far.

You may do larger than 50% weekly if you wish once every month etc or each week etc if you so chose.

I tend to do larger water changes, clean things real good, stay on top of things well when I have any issues pop up.

Mild BGA really is not a blackout or Antibiotic issue, it's typically solvable with CO2/Nutrients and good cleaning a few times, vac the substrate etc.

Tom Barr


Guru Class Expert
Jan 6, 2006
I can confirm it work better to dose many time than once a weak. before I dosed my ferts once every weak for Co2 tank. result were not bad but I had algae once in a while and allwais green spot algae here and there.
Now, I dose macro every 2 days and micro every other days. it work just way beter.