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The estimative index
- To: <Aquatic-Plants at actwin_com>
- Subject: The estimative index
- From: Thomas Barr <tcbiii at earthlink_net>
- Date: Mon, 15 Apr 2002 22:30:00 -0700
- In-reply-to: <200204140748.g3E7m3A10468 at acme_actwin.com>
- User-agent: Microsoft-Outlook-Express-Macintosh-Edition/5.02.2022
I was responding to someone about dosing recently and came up with a
clearer(I hope!) way to explain this idea and method. It's long but I try to
cover most of the bases.
#1 Dosing. This can be very tricky when dealing with many variables. Often
the suggestion is "buy a test kit" and test to see what your nutrient levels
are. This works well for CO2(but folks should double check to be sure before
proceeding on) and GH but the other nutrients like NO3, K, PO4, iron as a
proxy for the traces are more problematic. Chuck Gadd's dosing calculator
works well for the chemistry challenged.
2# Testing. This is huge issue for most folks. Test kits cost as much as a
filter or much more in some cases. Some folks can afford nice Lamott/Hach
kits, most cannot nor wish to invest 300$ in this. Cheaper kits are not
offered for K, NO3 kits are very problematic and color reading scales are
difficult to assess with cheaper kits. Some folks are color blind. Many
folks don't ever want to test and/or feel there's no need to test. Iron (Fe)
test have been a very contentious issue for me for about 3 years now. I
believe I have a relative simple methodology to side step much of the
At issue here is the maintenance of the nutrient levels. The focus will be
on 4 groups, nitrate(NO3), phosphate(PO4), potassium(K) and the trace
elements represented by iron(Fe) in a mixture with the other trace elements.
Perhaps a better question is how close to a good range of nutrients do we
have to be to have excellent plant growth and no algae?
Using an "estimative index" the accuracy can be as follows:
(+ or -) 5ppm of CO2 is fine in a 20-30ppm range.
(+ or -)1ppm or so of NO3 is pretty reasonable.
(+ or -)2ppm of K+ is pretty reasonable.
(+ or -) 0.2ppm of PO4 is pretty reasonable(?)
(+ or -) 0.1ppm of Fe is reasonable(?)
CO2 range 20-30ppm
NO3 range 5-10ppm
K+ range 20-30ppm
PO4 range 0.4-1.0ppm
Fe .5ppm or higher(?)
PO4 and Fe are two nutrients that are difficult to assess without first
assessing the other nutrients. If the NO3, K, and CO2 are in good shape, you
can add a fair amount of these within a wide range. I have added to almost
2ppm of PO4 consistently week after week. Plant's response is incredible.
Adding traces has been a focus for me lately. Many have stuck with the old
standby of a residual of 0.1ppm of iron. Well what does this residual tell
us? Does it tell us what is available to the plants? Is this enough? Does
higher dose when the other nutrients are present cause algae?
I can tell from my own experiences that high levels of traces(Fe) have in no
way contributed to any algae presence. I made sure and double checked the
other nutrients before drawing a conclusion. I've gone around and around and
have used Sera, Kent, TMG, Flourish and now recently the PMDD's "Plantex" at
2 tablespoons in 500mls of DI water to see how far I can push things. At
some point the plants will not take up any more traces. Same can be said for
PO4. Adding more simply will not improve plant growth any further. This is
where the top end of a range should be. No need to waste expensive trace
nutrients. Folks that have had issues with algae prior may want to try
adding the PO4 and then adding more traces in conjuction. Claus had
mentioned that many folks in the sfbaaps group had too low trace levels and
that they needed to add more which most did and were very pleased with the
outcome. I had been dumping in a load of traces all along since my reference
sometime ago had been Karl Schoeler's .7ppm recommendation and I felt like a
little more might help if the tank was doing well as many recommendations
seemed middle of the road. Although I had tested numerous times and tried to
look for some correlation with the test kits for uptake, I became less
focused on the testing aspect and came up with what I think is a better
method for the traces. I still contend _most folks_ under dose the traces a
The estimative part:
Simply adding a set amount of traces to a known volume of water. If the tank
has less plants, low light, this can/may be reduce in frequency but not
dosage. A similar pattern can be done for the other nutrients. In this
manner you essentially are making a "reference solution" each time you dose
and you assume a certain amount of uptake the other one or two times prior
to making a large water change at week's end. If you have low plant density
or have low light(two watts or less NO FL's) you can get by on once a week.
By knowing what the tap water is comprised of and giving the water company a
call to find out what the PO4, NO3, K, and Fe levels are, you can replace
the water with water changes and use plain old chemistry or Chuck's
calculator to figure out what you need for your nutrient levels without a
Even if you are off a little that's okay(see above's +'s and -'s). The water
utility will have some variation but if you are close to the middle ranges
it should still come out fairly close.
So imagine a tank where you don't test except for CO2(pH and KH) and only
that once in a while. Everything grows well. No guessing.
Basically you are making a crude standard reference solution every
week and topping off the plant uptake. Even if you are off a tad it's
not going to cause problems because plants/algae are adapted to a
range, not one specific level. You can extend this method out to
include all the other nutrients like traces and PO4 even KH and GH.
End of the week, you remove the nutreints and re set it all overagain.
So for at least a few days every week the tank is "perfect". You can
try whatever you feel is "perfect" for plant growth and experiment
Good sized weekly water changes are an excellent way to do this and
avoid build up and any **dosing** errors or **testing** errors. Test
kits(good ones) are not cheap and many are too lazy to use them:-)