We at APC do not normally step in and edit posts or split threads with out a reason. We feel that Discussion of the PPS Method warrants it's own thread and should not be mixed with the actual article.
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Water, fish, plants, biology and ones individual ecosystem that are created in your rooms are not standard, they are not the same, and they are not generic. Each has a life of their own and each is unique in both design and water chemistry. Accordingly, the Perpetual Preservation System was born from this idea. The idea that your tank is different, the idea that your tank is unique and that it requires unique attention is what brings us to where we are today in terms of aquatic plant fertilization and maintenance.
Are they really unique as far as their needs?
Plants need the same things pretty much, Light, CO2 and nutrients.
Assume maximum rates, then anything less than that will still have a good supply(eg non limiting)
Not that unique..............
Routine mainteance/water changes can standarize things for everyone everywhere. Actually they have and have for some time.
If you add "just enough" for your particular "unique" tank you end up walking a razor's edge. While it's possible to add just enough with time and skill and watching the plants a lot, it also requires lots of testing, RO water, calibration of your test till you get a feel for your unique tank.
I've done this, so have many many aquarist before you.
Reef folks do this and I keep those as well.
I hear their sufering quite often, meanwhile I do a simple water change and don't need to do even 10% of the expense, time and work to have the same results.
This introduces a large amount of variables and work.
Over the past months I attempted to get this point across in many posts here on APC answering a question at a time, a parameter at a time, a topic at a time which caused confusion. Your aquatic systems are not standalone; they can not be analyzed alone, they must be looked at in its entirety as a whole.
So go from light=> CO2=> NO3=> K+=> GH=> PO4=> Traces
If those are addressed, that's pretty much all plant needs.
The rate of uptake and light(or CO2 or NO3 or PO4) that drives the system relates to the balance. This is true in marine systems, non CO2 plant tanks, lakes/ponds, rivers, anywhere there is good plant growth.
You can test each individual system and find some it's unique needs and dose accordingly.This involves a lot of testing. Many will never do that. The other issue, while testing is useful, the rates of uptake depending on biomass changes, pruning, water dosing errors etc make testing a long term project.
You will slip up and neglect a tank at some point. Adding more things and steps make this far mopre likely.
Simple is good.
After some time, folks can use their plants as indicators to see that things are fine or need work. Or they can simply go on as they were and waste a little trace/KNO3/KH2PO4. That's dirt cheap. But then it gets back to testing again. You chase the test, why wait till something is getting too low? Why wait till you start to see holes in ther M umbrosum? Some folks get good and can predict this before it occurs by watching the growth rates. That's not something that is easily learned or shown to a new person, it's learned from screwing up and trying to anticipate. Or you can test (and hope you tested the right thing/reading, be sure to calibrate etc).
But to what end? What do the test show you? Why are you dosing these nutrients to begin with?
To maintain a stable nutrient level for the plants?
To see what the plants use?
I understand the PPS, correct me if I am wrong, to mean few water changes, use only when needed or things get out of whack. Then dose and test to replace the nutrients as they are used up.
Add just enough nutrients.
Many will not calibrate their test kits. Many will neglect testing and slack off.
Many will not prune for a long peroid, many will not be able to afford or otherwise spend the $ on the test kits. It's asking a lot from someone for what?
Diana Walstad's arguement for the non CO2 method is extremely strong in that regard. No kits, no water changes, decent plant health, growth etc. Low maintenance. Supply of nutrients(fish food+ some from the substrate initially)=outputs(plant pruning). I differ with her on some points, but the overall notion is very very strong.
TE build up can cause a number of problems, we see this is reef tanks with Cu, they also, much like this, try to avoid water changes and dose only what is needed. They also do a heck of a lot of work to achieve this and at a considerable cost. Do you test for Cu? Or just Fe as proxy for all the TE?
On your dry weights pie wheel, 13% is NO3? NH4? or Total N?
My references are about 1.5% N.
I'm still trying to find some utility beyond fewer water changes.
I know you have put a lot of work into it, been there done that, still do that, but what is the goal? Good plant growth with the least amount of work? I did all that testing for years and still do it, but to answer certain questions. I want something out of my work.
Otherwise I'm doing the testing for no real reason other than to avoid a few simple water changes. I tried that. At lower light it works fairly well, any system does, I don't do any water changes of the non CO2 tanks. If I'm going to do the work and go through all that, I want something out of it. I used the rates I learned from the testing on many tanks and plant species(close to 250-300 now) to determine a simple dosing method using water changes and tap water.
This works on just about any tank, from Zambia to Australia. It works because it addresses these unique differences by assuming the tank at max light. That covers all the bases, but assumes that the higher levels will be fine, this proved to be fine regarding algae and toxicity levels build up for all the nutrients and organic by products that reduce O2 levels, not just one trace element and the kits you have on hand.
Then folks can reduce the nutrients down to suit their unique needs based on plant health, rather than testing. Water changes with tap water are easy to do, then dosing thereafter makes it easy. That answered my question and solved this issue without the need for test kits, without introducing a huge work load, without so many unknowns and expense to the hobby. It is good to test for some things to reduce the amounts of KNO3 you may need, I have a good feel for various light levels and rates of uptake, CO2/non CO2 approaches. Yep, it took many years and work and discussion as well.
I'm still not clear on what your goal is here besides reducing water changes through lots of testing and long term reliance on the test kits. Can you discuss that aspect in detail and the reasoning behind it?