The bottom line is really this: test a single variable at a time. So if you subscribe to Liebig, Mg seems like an easy obvious candidate. Bsmith has an opportunity to see if this is true, vs any ratio or multiparameter variation.
I could less if monkeys fly out of hind end if I am right or anyone else......however, I'd like to know if Mg is something to look at more in depth, there's correlation there. If I am wrong, we move on to the next likely group of suspects. I'm not going to hang on to it if it gets falsified.
Bsmith and others have an opportunity to test this, I do not. I'd rather not see that wasted and not be able to say much about which variable did what.
Was it the ADA AS or was it the powersand?
Was it good overall conditions, or was it the heating cables?
You cannot tell unless you test each variable and combination.
MCI might have had a few successes, and few folks using EI might have as well, I see no reason why both observations cannot be true. We cannot say why they failed or not, or at least offer some evidence to that effect unless we attempt some hypothesis that are specific, like testing Mg increase dosing. This is an easy low picked fruit to try out.
No good reason not to try it in other words.
Makes sense if you focus only on plant growth - as I know you propose. Mg could be limiting plant growth and giving GDA a foothold, I think the arguement goes. However, my plants always grew incredibly well during the GDA outbreaks and when I did scrape the glass I would see my overgrown jungle waiting for a trim. Didnt slow the algae growth.
As we've seen with other types of algae, there are certain predictable water parameters that bring on certain types of algae. In my tank, if I let Nitrate drop below 5, I know I am going to start seeing BGA. No other types of algae appear. So, according to the plant growth focus, my plants must be growing more slowly and allowing algae to take hold - but why only BGA? Why dont they all come on at once at this point?
To me, this supports very strongly the idea that, while healthy plant growth may inhibit algae, it cannot stop all types of algae. Also, there are certain nutrient threshholds that must be met for the ever present algae spores in our tanks to bloom into visible algae.
I know that plants dont know math and ratios are laughed at, but we do know that certain excesses of nutrients in the water column create plant deficiencies for other nutrients, even if the other nutrients are present in the water column. How then is it unreasonable then to think that certain levels of a nutrient in the water, relative to another nutrient would INHIBIT ALGAE GROWTH (not increase plant growth, inhibit algae growth - big difference)?
Going one step further, how then would it be unreasonable to assume that a 'complex' relationship could exist that inhibits GDA? Meaning, that GDA will not bloom unless there is an excess of Ca vs Mg OR an excess of N to P? In this case, changing and monitoring one variable at a time may never lead you to the result you want. Ie if your N and P ratio is put of whack and you are just adding Mg, you could get your Ca:Mg ratio inline, but becuase your N:P ratio is still of whack, your GDA does not go away. You declare your Mg theory debunked and go on to test N:P and your Ca:Mg drifts back to out of whack. You get your N:P ratio right, but stil GDA becuase you're no longer considering Ca:Mg.
More complicated still would be some combination of absolute minimum level and ratio (ie Ca:Mg must be no more than 3:1, N:P ratio at least 10:1, Ca no higher than 40ppm, and P no higher than .25 ppm in order to prevent GDA bloom, for example).
Solution is to change and track multiple parameters through multiple ranges and see when you get GDA (maybe more even than just Ca, Mg, P, and N - I suggest these only because the MCI author proposed them based on his experience and they are the two i monitored and changed to eleviate my problem - could be more involved and i just got lucky). I suggest the reason we've not as a hobby solved this one while other algaes are more easily controlled is exactly becuase of some kind of complex relationship between the parameters that cause it.
Aside from somone taking a few weeks, and tracking all parameters through all ranges in a few quarantine tanks, we'll probably need to keep tinkering and collectively building a model. But one paramater at a time may not be the answer and focusing on strong plant growth as opposed to algae inhibition will only miss the mark.