What you say is true Carissa, but isn't the point of EI, to have a standard dose and not worry about measurements and uptake rates and exact numbers? If you did want to maintain exactly 30ppm levels in your tank, then you'd need to do what you say. ie, dose 30ppm right away and then if you know your plant uptake rates and have done extensive testing, then dose accordingly to compensate for the uptake rates.

I guess with EI the idea was to move away from being exact. So if you don't think that your plants are going to have an uptake of over 30ppm in a week, then this strategy should work fine. As long as you still have enough nitrates in the water for the plants not to be limitted by them, it should work well (As far as I understand).

Point taken. I think uptake rates are still important though even if you are doing ei, at least to some degree. If someone were adding 30ppm of nitrates every week and the plants were not keeping up, you could get nearly up to 60ppm over time. I've heard people say that this is not toxic, but I've lost fish at 40ppm from overdosing fertilizers accidentally. On the other hand, if the tank is very full of fast growing plants and co2, only dosing 4ppm per day may not keep up to demand, this has also happened to me (a calibrated nitrate test kit showed that my nitrates were 0, two days after adding 20ppm). Not that extensive testing is needed or at least not that often, but it can be guessed pretty reasonably by looking at your tank setup (co2, lighting, amount of plants, type of plants, fish load).

Also, there are some things that you might want to maintain at certain ppm's, not just >0, such as calcium and magnesium. These should just be added weekly at the dose that you need to bring the tank up to the level you want, if you need to add them. Granted this is not the same as fertilizers that get used up quickly.

EI was set up to be "Fertilizing for the Lazy", or maybe "Fertilizing for Dummies". You have a choice of using EI, which means looking up your tank size in a table, then dosing per that table, followed by changing about half of the water in the tank every week. Or, you can measure what concentrations of the various nutrients are in the tank, calculate how much of each fertillizer is needed to increase that level to some "target" value, dose, measure again later, dose again, etc. If you enjoy doing it that way you should do it that way. Many people do enjoy the chemistry of keeping aquatic plants, and enjoy trying to read the plants to determine what is possibly in short supply, calculating what needs to be added, etc. Those people should do their fertilizing by a method that they enjoy.

Tom has pointed out that EI dosages are not cast in concrete either. They are supposed to be enough to cover the plants needs for any reasonable plant load and light intensity. But, that means they are more than necessary for many tanks. He has suggested starting with the table amounts, then gradually reducing them until you see an adverse effect on the plants, then going back to the dose that didn't give that adverse effect. That is the "semi-chemist" approach - EI Pro, I guess. I happen to fit the original description of the plant keeper the EI system was designed for, so I just follow it.

Test kits are not exact and few use them to any degree of accuracy anyhow.


There is a large amount of hypocrisy with folks that insist that we test to maintain good conditions and precise tolerances for ppm's when they themselves do not measure correctly to start with.

I'm a bit more honest about things.
They want to get lost in their own pre drawn conclusions, that's their business, but they will never win a debate.

Some common sense should also be applied, plants can and do grow in wide range of nutrient ppm's. It's not a pre set ppm with no variation.

If someone really wants to do this, I can certainly help them do it, but they might not like how far they need to go to achieve that goal.

And that's the rub, they wanna do a lazy short cut while telling folks to do all this added labor because it's "needed". When you start taking lots of short cuts, there are trade offs, you start losing the very thing you claim you want to achieve.

So where is the balance?
EI does this well.

You can reduce the labor of water changes using some test kits if you want.
You can also not do either water changes or test kits and eye ball the plants.
You can add ferts to the sediments, AS, mud, etc, and not dose much, or go lean in the water column with rich sediments(ADA's and other folk's approach) and no test kits. However, ADA and other folks still suggest large frequent water changes

And poor CO2 will doom any method here and folks often blame the dosing, not their poor use and extremely poor measurement of CO2 and general high light

And around and around we go.
History repeats itself way too many times here in this hobby.
They assume huge liberties with light and CO2, without any critical investigation, then blame nutrients, or ADA, or themselves("I just cannot grow plants"), EI, PMDD etc.

All while using poor test methods and cheap 6-12$ test kits.
You can get some accuracy out of some test kits that are cheap, but some you cannot.

We all get lazy and take short cuts, but a wise person will realize this and set up a method to reduce the trade offs.

I do not like water changes either, but I set things up to automate or make it really easy for myself.

Then no test and no labor involved for water changes.

That's a truly lazy and smarter hobbyist.

Then it's most gardening goals.

Regards,
Tom Barr