Yes, thus the "some...all..." reference in my post. In any event I was probably overspecific since some cyanos, including Oscillatoria species, have been shown to fix N2 w/o heterocysts.
Not the species we have though..........do you know how the other species do this without heterocyst?
Did you induce NO3 or did you induce Oscillatoria?
And no, I'm not trying to be an ass thinking I'm pointing out a typo, I'm actually curious if this is what you meant. E.G., there are published reports of limnic eutrophication resulting from nutrient addition of N and P, but not directly a result of algae blooming on them, rather hetero bacteria blooming thus oxidizing C and providing CO2 to the algae. So were you trying to point out that you induced cyano by starving the tank, or point out that you increased NO3 by starving the tank?
The BGA, not NO3.
Here is my point: time and again, someone will post on the forum "I have this algal problem" without bothering to do a simple search, and some well-intentioned and fairly patient person will respond with the boilerplate "BGA = low nitrates." Which you admit is based on: 1) a correlation (qualitatively stated as "strong") of solved cases to reports of cyano, and 2) a lack of convincing data regarding the real culprit being a) K or NO3 deficiency, b) the death of cyanos/algae via blackout releasing their stored nutrients to the plants, or c) another part of the unspecified "etc" you use as a treatment. All of which I could just as well criticize you about lack of control in these anecdotes as you argue with me about mine.
Then the original poster may come back and say "my nitrates are 20-30 ppm" and there'll be me who says "I have no BGA and my nitrates are basically zero (meaning unmeasurable with available equipment)." These are falsifications of the hypothesis.
Are they? Are the levels in their tank really 20-30ppm? I've seem many test kits measure that range when I use a calibrated accurate test method= less than 1ppm.
And just because you had a case where no BGA was induced, your test kits are also suspect.
So......you are making many bad assumptions here without supporting them while trying to argue I am not supporting mine.
For in order to be true, an hypothesis should match all observations.
Sure, assuming if
your assumptions about the NO3 levels in your tank is correct and that you have only and solely NO3 limitation and not other potential limiting issues, sediment nutrient sources or dirty filters and other possible reasons for BGA inducement.
And, yes, I know we are dealing with biological systems here so the best science we can hope for is matching X to Y compared to control group Z and nothing will be 100%. But the other fun aspect of an hypothesis: It also needs to make testable predictions. An obvious one in this example, "Plants will show signs of nitrogen deficiency." Do they? Another one would be "Adding more NO3 to the exclusion of any other nutrient will alleviate the cyanobacteria." Does it?
Well, plants past nutrient status do play a role, if they have been fed well, they will take longer and some species express it sooner than other.
I think the thing that gets me most is the absolutist nature of the statement "BGA = low nitrates." You insinuate that you think it is more a reaction of the plants to being stressed rather than a particular condition, yet from my interpretation of your post as a whole you still seem to defend the overall notion of lacking NO3. I am confused with the inconsistency. Now there is nothing wrong with saying "If you have BGA, check NO3 levels, as this has shown to be a common indicator of plant stress inducing a BGA outbreak." But "equals?" No.
Humans like simplified ideas, to make sense out a complex world. Uncertainty bothers folks.
I too have observed BGA in high NO3, but I've noted many times that it tends to be more common in low NO3 conditions with high light. Dirty filters, low flow, gravel line BGA etc can be present with high NO3, especially if the NO3 is derived from fish/plant rot waste.
I've never said BGA is due to one thing.
Most of the time if the filters have been cleaned and good CO2, etc, then low NO3 is the most common indicator.
Regarding my confidence in determining NO3 levels: yes they are based more on just "not dosing" ferts.
So the blind man is questioning what I see?
I don't have my own KNO3 supply, so here is how I "calibrated" my NO3 test kit(s). First, I tried kit#1. It read 0 and I expected it to read higher than that, so I thought to myself "Oh, this kit is too old and doesn't work properly" so I went and bought kit#2 of a different brand. Same result = 0. A little "wtf" went through my head. So I brought in a sample to the LFS, they tested with a dip strip. Result = 0. So I figure, if the chances are that all 3 different kits provide the exact same false reading, the universe has it in for me and whatever consequences I have coming as a result of believing them are unavoidable. But, using your words, generally the evidence points towards my NO3 = "0."
No, that is all you, all your own assumptions.
You are unwilling to do it right and want to question the basic methods used to determine/refute the hypothesis.
You can still argue, but you have no foundation to base it on.
We are not on equal footing here.
I have done the test in a critical manner using inert substrates.
And I should add that I used an inappropriate term in 'starve' regarding N & P with my plants...they actually have those elements available via root tabs.
Now you are getting yourself in such a pickle.
If you assuem water column nutrients are low NO3-BGA etc, then do you not think this totally confounds the idea?
If you where using, like I did, inert sand to make such determinations, you might see a different view.
You have all sorts of confounding factors that you have not addressed and want to suggest that the hypothesis is flawed based of them.
When you are able to master the testing methods, the dosing and experimental design, you can haggle.
Till then? Not with any confidence.
I just see no reason to tell a person who asks, e.g., "My NO3 is < 5.0 ppm, is this a problem?" that they should expect an outbreak of cyanobacteria.
Nor do I.
It may depend on a great many things, the first of which is the assumption that their tank is really <5ppm of NO3.
I do not approach solving folks problesm that way though.
Or telling a person with "BGA" that that is definitively what their problem is.
After solving a lot of folks probelms consistently, perhaps better than anyone else in the last 15 years with respect to algae, I have a a good record. It does in no way imply I am correct though. It does give me a lot of experiences to draw from and a lot of testing, testing errors and assumptions as I have made a lot of mistake to understanding what is occuring.
That is how we learn.
But.....while I do not reject other possible mechanims for BGA blooms in our tanks, I do see a very high likelyhood of low NO3 and the potential cure by adding KNO3 back.
No, not everything is possibly known about BGA in our tanks nor will it.
But a lot more is known today because I went through and did the work and folks have much lower occurances when they follow the routines I suggest.
There is strong correlation, but cause is quite another matter to prove.
1. Test kits, you need to learn how to calibrate and measure and become a lot more accurate and have fewer assumptions there.
2. Substrate water column sources of N and P nutrients, obviously you need to address this as well.
3. Test replicates you based your theory on one tank without controls of any sort nor verification near as we can tell.
This takes time and a lot of work.
I do encourage you to go forth and disprove/prove things, but you need to be able to say something if you do this work and leave no stone unturned in the search. If you overlook things you do all this work and find yourself unable to say much one way or another.
I see this all the time.
But the basic notion that BGa blooms maybe caused by other things than low NO3, I most certainly concede, but it's not due youer arguements presented here, I already conceded that a long time ago.
When someone's BGA is not addressed via KNO3/Blackout Antibiotics etc, then we go after the filters, or before even, just to rule things out.
Sure, they might do fine with very low NO3 in the water column, but they may have plenty of NO3 in the substrate.
In that case, the plants are still fine, it's not solely the water column that controls the BGA, it's the interaction between the N limiting of the plants and BGA and perhaps the NO3 levels as well.