Green Dust Algae

neilshieh said:

water params? GDA sometimes occurs from nitrate swings.

Click to expand...

I have found no support for NO3 swings.
Also, swings is non descriptive.
In other words, it's not helpful without real ppm included, say going from "4ppm to say 30ppm".
Or keeping a range "between 10-20ppm"

That's useful, "swings" does not tell us much, we learn little.

I've gone farther, but there's little point. Also, sediment ferts sources are not included for N.
Since my ADA As is old, it's been tested and has little available N.

So while the water column might have a lack or a swing of N, the sediment very well may not.
Without measuring it, hard to say.

Plenty of folks have tried in vain to do lots of water changes and many have not dosed after to see if any effect occurs....this is met by failure as well.
Adding NO3 also did not seem to have much effect.

Since I have 5-6 tanks and only the ones with the CO2 has issues, I find it difficult to support NO3 swings, since all tanks got the same KNO3 dosing and only one tank , the one with poor CO2, ever had or could sustain GDA.
Repeated inoculations prove fruitless to the other tanks with good CO2. GDA is rather harmless to plants, so such test have little harmful effects on plants. Same for GW.

I can rule things out, but it is tougher to assign blame to CO2.
Still, I cannot falsify CO2 at this time.

Since I have several tanks: I can measure the light in relative terms of PAR, measure CO2 with high accuracy, Dosing is rather a simple affair, I can look at the whole picture.
I know the sediment for the most part and have tested the ADA, the Flourite and plain sand are fairly easy to look up as well. So things are fairly independent between the tank except the CO2.
Adjusting it.......and the GDA has never come back.

I also tried something else, I took the CO2 off.
This knock it back.

I think some have tried adding peat, that seemed to work as well.
But at the root, the CO2 seems to be the biggest factor.
Higher light seems to exacerbate all algae issues.
And more light => more CO2 demand which would also support observations also.











Regards,
Tom Barr

I figured it'd be better to bump this than start my own thread...

Today I finally gave in and cleaned the glass of my plant-free African tank. (Took forever!) It had GDA but 6 weeks of leaving it alone didn't do anything.

Did I mis-diagnose? It seemed to be pretty obviously GDA. Nothing like the spot or any other type that I know of. Very hard to scrub off, turned the water green, etc...

It started in this tank when I temporarily had some very powerful lights (from an old planted tank) over the tank for about 2-3 weeks. It nearly tripled the usual output, and even though I went back to the usual amount afterward, the GDA remains.

Today's scrubbing came during a WC that was as close to 100% as possible (once I reached about 20% remaining I had one python filling and one draining for quite a while til I finished scrubbing), so I suppose maybe there's a chance I got rid of a lot of it... but I doubt it. There's still plenty living on the rocks and the back glass behind rocks. I'm sure it'll be back.

So... now what?

I tend to agree with the phosphate method. I had a GSA problem in my main tank, and upping the phosphate coupled with the occasional scraping before water changes has knocked it back to almost nothing. I can't say that there is a direct correlation with P dosing, but it did work for me. Currently, my grow out tank is starting to show some GDA issues which I haven't sorted out yet. (This tank has a 12hr photoperiod, which is not going to change, so I have some thinking/experimenting to do.)

Let me stress that this is a general trend that occured over several months, and P dosing didn't eliminate GDA immediately. Also, the tank isn't totally free of GDA. If I were to go a couple months without cleaning the glass you would be able to see the haze. There are some spots in the back also where I can't clean that still have the old GSA that I never removed around driftwood, etc (it didn't die off with added P). Some spots did die however, leaving what seems like a calcium or silica deposit behind.