EI with less than 5.5 W/gal

[FrankG]

Tom,

I am not sure if this question has ever been asked and answered:

In your EI article, you write:

A typical routine for a high light tank with low fish load:
Volume 80 liters (20 gal high standard tank)
5.5 watts/ gal. - two 55watt 5000K/8800K lamps
...
1/4 teaspoon of KNO3 3-4x a week (every other day)
1/16th-1/32nd teaspoon of KH2PO4 3-4x a week (every other day)
Traces added on off days as the macro nutrients, so 3x a week, 5mls each time.
SeaChem Equilibrium 1/8 teaspoon after water change.

Well, what is the relationship between the dosing amounts and the light? Let's assume I have 3 W/gal PC, how would you start? Obviously, you can reduce your dosing, but how much is safe? Would you reduce the amount or the frequency?
I played around with the amount and eventually got there. But I wonder if there is a better starting point, if you have less light.

Thanks,
Frank

 

[Tom Barr]

Re: EI with less than 5.5 W/gal

Simple, you can not reduce the levels at all.

You always desire an excess amount of CO2/nutrients at all times, not "just enough", having another 0.5ppm of PO4 or 5ppm of NO3 is not going to hurt anything in any tank.

You can also add less slowly, say adding 3 ppm less for each 3 week peroid for NO3 til you get a negative response from the plants, this takes time though, and the needs of the plants do change as plant biomass changes and we prune it back etc.

Main thing is to provide ample nutrients at all time, so the high light idea works, wereas trying to dial in each individual tank's uptake rates, which do change as plant species and biomass change, is a quagmire that requires a lot more testing.

Rather than getting bogged down with the test kits, dosing, huge methods etc, simply use the plant as the test kit and slowly decrease the nutrients progressively till you get a plant response.

This is called a phytometer, basically using the plant as test kit.

Which is what I've one mainly all along anyway

Regards,
Tom Barr

 

[FrankG]

Re: EI with less than 5.5 W/gal

Tom,

Simple, you can not reduce the levels at all.

Not sure we are talking about the same. I do not want to reduce the levels in the water column, but with less light I would expect to need less dosing to achieve the same nutrient levels.

You always desire an excess amount of CO2/nutrients at all times, not "just enough", having another 0.5ppm of PO4 or 5ppm of NO3 is not going to hurt anything in any tank.

Again, I do not disagree. Actually, I would even say that is the beauty of your findings and EI. But how much excess do I really need to be safe? Again, with less light I would estimate less dosing will achieve the same excess amounts of nutrients. I would not even touch the CO2.

You can also add less slowly, say adding 3 ppm less for each 3 week peroid for NO3 til you get a negative response from the plants, this takes time though, and the needs of the plants do change as plant biomass changes and we prune it back etc.

That is how I did it and that is how I found out that about half the amounts were about right for my tank. And I still have excess nutrients based on my TDS climbing slightly between water changes. If I had started with 2 dosings per week (instead of 3), I would have wasted less nutrients in the beginning. Not that they are that expensive, but I just don't want to go really high on my NO3, PO4, if I don't have to.

Regards,
Frank