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[APD] Re: Aquatic-Plants Digest, Vol 4, Issue 46

"Now I am searching for the "right" nutrient levels. I know it is like
searching the Holy Grail, but there must be studies of the optimal
conditions for aquatic plants. You can find the basic things from the
internet, for example: NO3 3-5ppm, Fe 0.1ppm. But what about the rest?
Does anyone know any good sites?"

Well why do you NEED such a tight narrow range?
Do eat a certain amount every moment/second?
You need enough food to feel fat and happy and you need food at regular internvals.
Plants are fine either of these methods, but it's 100X easier to feed them every 3 days or so.
3ppm of NO3 will last about  a day in a well run tank.
About .3-.4ppm of PO4
K+ I tend to estimate based on Epstein (1972) which is about 2ppm a day.
Fe if you want to do the same thing, will be about 0.006 ppm(Roughly 500 times less the Nitrogen level) or so a day.
Others are less, there is no kit unless you are a very well equipped research oceangraphic facility that can test the micronutrient level in these ranges.
Fe and NO3 test kits are mighty contenious issues for me, I have not found any iron kit that tells me how much iron is needed for the plants. I can get a measurement in the water but that level does not tell me if the plants are gaining or getting anything from this level. 
You are simply better off using your eyes when dealing with how much trace you need.
Keep the macro nutrienmts ina good range, then vary the milliliters of trace you add, say 5mls per 200 liters every 3 days, do that for a 3 weeks and note plant health.
Then try 10 mls per 200 liters each 3 days and note plant health and so on..........
These ratios above will vary plant to plant.
There is a range if you start at zero ppm and steadily increase concentration that is best for the plants. Below a range of NO3 of less or near 1-2ppm is typically too low, you want more for the plant to be happy. Above 15ppm or so is more than enough for the plant for a few days.  What you do not want to do is to let the levels drop down to zero for more than a day or 1.5 days.
Traces are fine, but the macro's you do not want this to occur longer than a 1-2 days.
So what to do? 
Well do a large water change, find out if your source water has NO3 and PO4 in uit and how much. 
So if it's fairly clean, then you assume it to be zero ppm of PO4/NO3.
Well if you do large frequent water changes, then your tank will have very very low levels of these, no tannins, no humics, no organic components and other things you do not test for.
So you add KNO3, KH2PO4, K2SO4 and traces.
After each water change you have a standard solution almost(well whatever of the % of the water changed will be referenced).
Basically you do large weekly water changes to remove any excesses and re set the tank and then you estimate/guess the next 1-2 doses in the mid week.
You can also "mega dose" right before a water change. This involves dosing 2-3x the PO4/NO3 about 24-12 hours before you do a large water change.
The dosing prevents anything from running out while the large water changes prevent anything from building up.
In this manner, one can maintain a good range of parameters without doing hardly any testing ever.
pH should be monitored closely and KH/GH every so often.
Other than that, not much else unless you are curious.
You can see the DFW site:
"This is starting to sound more and more ridicilous with every line I write,
but well, someone has to ask the stupid questions too :)

-Satu Jäske

Satu, these questions are not stupid, about 8 years ago this was what got discussed here everyday almost.
Everyone was in the dark back then. We recently got a lot of things worked out.
Tom Barr

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