Varying the CO2 often/rapidly/up and down"confuses" the plants enzymatic machinery, and signals environmental change for algae spores.
If the plant has low CO2 stable conditions, it will produce a lot more Rubsico to take up the CO2 that is there. It will downregulate growth and other pathways.
A plant is large lumbering organism compared to the algae.
It takes a while for the plant to adjust.
That's the break the algae spores exploit, with each other and with plants which make great places to grow for them.
If you have high CO2, why produce all this extra expensive Nitrogen rich enzymatic machinery? You do not need it, so the plant degrades it and increases other pathways to account for less demands for growth and maintenance, so it upregulates growth to match the environment.
It has an optimal environment in both cases, but the growth rate is slowed due to low CO2.
About 10x slower.
And that's about what my test predicted for a non CO2 water column dosing approach when I measured the parameters.
You can simply measure NO3 if you are concerned. A well run non CO2 planted tank will achieve balance, but that does not mean no work at all, just well managed work.
Ideally when you measure NO3 say once a week or once a month, you should measure right before you planned on dosing and you should read 5 ppm or less, most well run non CO2 planted tanks run near 0ppm.
They can handle low levels as the plant growth is greatly reduced by an order of magnitude. So as the fish and bacteria/dead plants leaves produce NH4/NO3, it's used up.
So you never measure any, it's assimilated before you have a chance to measure it.
So the tank can appear to run without any measureable NO3/NH4 at all!
Note, many older test about growign aquatic plants suggest very low N and P levels for best growth.
Such balanced tanks seemed to have this trait, while others that had constantly rising NO3, had algae issues(due to NH4, not so much NO3 levels).
This explains a great many observations/correlations that folks made assumptions about in the past. These folks where smart also, but they made understandable, but wrong assumptions about the observations.
They needed to go back and add inorganic sources of nothing but NO3, rather than organic sources of N like too many fish, too much fish food, too much garden soil that had not been boiled or soaked a few weeks prior.
By the time they measured things, the NH4 had long since gone to NO3 and the algae was home to roost.
The crazy thing, at least to myself, was these same folks never tested their hypothesis, they just assumed that because everyone suggested that was the right theory, it must be right.
I mean it was very simple to add KNO3, it was very simple to add KH2PO4.
Then observe if it induces the algae spores to bloom or not.
You need to start with a relatively stable algae free tank and then perturb it with each variable and then both to see.
Don't you think that is a simple thing to do if you make such a hypothesis and given the fact so many have algae and you link it to those two nutrients?
I'm still amazed no one ever did that and some still suggest these cause algae.
If you make a claim that high NO3 kill fish, and we should not dose KNO3 because of that, you need to show cause/correlation and test it to show support.
I have/did and have not found any support, I've found the range to be enormous.
Same for PO4. Same for K+. Same for Traces. Same for GH. and as long as the CO2 is stable, the same for CO2.
Now I've added high amounts to non CO2 tanks also, I still was never able to perturb the tanks(4 of them) with KH2PO4/KNO3/Traces.
So they appear to be as robust in response to high nutrient levels as CO2 enriched tanks. Note, they have much better stability in terms of nutrients levels also vs the CO2 enriched tanks that remove nutrients 10x faster.
This mirrors the predictions my general theories hold for both CO2 and non CO2 methods.
The only caveat: careful not to overdose the nutrients and have to test, you can avoid testing altogether and still dose to a slight deficiency.
Plants take a longer time(well, 10X longer) to express a problem as they do in a CO2 enriched tank.
So if you are running low, you can see it and catch it over a 10-20 day time frame vs a 1-2 day time frame.
So the plants now become the test kit, or a phytometer.
You can find out how a plant responds to low NO3 by withholding the KNO3 dosing for a little while(add K2SO4 during this time) and wait and watch. See who starts acting squirrley first, then use that weed as your test kit to know when to add more KNO3.
Simple huh?
Not sure why the heck these folks don't tell folks such simple methods.
Sprinkle fish food and praying is not a good method, nor is a test kit, that just measures N it does not tell you really if the plant has enough N or not.
A plant will not lie, a test kit and our assumptions about them most certainly can fool you.
Regards,
Tom Barr
