# GDA - observations



## HiNtZ (22 Jul 2018)

I'd be interested to hear other people's observations/opinions on this stuff, and, what kind of setup they have.

I have suffered with GDA for as long as I can remember, always on day 3-4 it would appear then get worse by day 6-7. Personally I put it down to an overdose of some micro element (zinc, manganese??) - at least in my setup.

Tank: 150L
Light: 140w high intensity full spectrum PAR LED's
Substrate: Westland aquatic compost capped with 4" sand
Photoperiod: 2hr low intensity, 6 hour high, 2 hour low
Co2: Pressurised CO2
Ferts: Full EI

GH 7
KH 5
Water 50/50 RO/tap
Weekly 50% WC

I recently (about three/four weeks now) have stopped dosing micros and iron altogether. I figured I'll keep on with the macro as per EI & add a little Mg (about 5ppm at water change and a few ppm throughout the week since we're a bit low in the tap in London, especially as I'm cutting the water) and see how the substrate can maintain the plants.

Well, in the process the GDA has gone  I've not had it for a couple of weeks now, the week just gone being the best week yet - I hadn't actually noticed I'm not constantly cleaning the glass anymore. The plants are picking up in health too. I think I underestimated the substrate as it appears dosing any form of iron or micro nutrient (bar magnesium) really causes me massive plant health issues with the included bonus of GDA.

This was literally the ONLY algae I was suffering with while all the changes I listed further below were carried out. CO2, light and flow/filtration remained the same all the way through.

Not trying to say anything about toxicity or take any sides in the debate on what actually GDA is. I just want to know what people who have successfully got rid of it changed at the time. 
Some further observations:

Before reducing trace and iron, I tried everything else over the years...

Starving macros
Overdosing macros
doubling trace
trebling potassium
decreasing magnesium
increasing magnesium (interestingly this aggravated the situation ten fold)
reconstituting RO/DI (while I was doing this, the GDA would show up on day 6-7 with the same dosing routines, never earlier)
Using commercial liquid fert (profito) (again, an observation here was that the GDA showed up later when dosing this instead of the chelated trace mix)

Not sure why I never tried cutting the micros out (and foolishly even increasing them!) I was always under the impression the tap was light on that sort of thing, that and the evidently potent substrate I have in there. I didn't have the patience or the bottle to leave it a few weeks. I'd always add some micro by day 2-3. 

Really would like to hear what others have experienced.


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## rebel (23 Jul 2018)

If GDA is your only algae, you are lucky. 

For me it comes and then it goes. Its hard to know because otos and nerites make short work of it. Too much light definitely feeds it .


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## Zeus. (23 Jul 2018)

Left my GDA on the glass for a few weeks as was on holiday, then did a good glass clean up, several weeks later I did a mini rescape which resulted in a better turnover/flow in the tank and the GDA does seem to not as prolific as before not that it was that bad to start of with, even though I have turned the light intensity quite a bit since the rescape. The rescaped was with plants which benefit a higher light intensity in areas


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## HiNtZ (23 Jul 2018)

rebel said:


> If GDA is your only algae, you are lucky.
> 
> For me it comes and then it goes. Its hard to know because otos and nerites make short work of it. Too much light definitely feeds it .



I've had most:
BBA
GSA
Few diatoms in the beginning although apparently not an algae, same as GDA.
Stag horn
Brown thread

I managed to get rid of all of them with good maintenance, increased flow and CO2. The GDA is the only one this didn't work for.

I've heard a lot of people saying light is not a factor in its formation and I somewhat agree. Reducing lighting seems to suppress it for a day or two but that's it (at least for me it does). As soon as I learned that light wasn't a major factor in the source/cause of the GDA but was more an enabler, I decided to leave them full blast and attempt to solve the problem by other means. 



Zeus. said:


> Left my GDA on the glass for a few weeks as was on holiday, then did a good glass clean up, several weeks later I did a mini rescape which resulted in a better turnover/flow in the tank and the GDA does seem to not as prolific as before not that it was that bad to start of with, even though I have turned the light intensity quite a bit since the rescape. The rescaped was with plants which benefit a higher light intensity in areas



I tried the two week wait and clean. It just came back worse. Forgot to mention this in the original post.

As for flow, I noticed more GDA in the areas of flow than those with not a lot. Also was never on the ends of the aquarium, only the front and back panes.

This is good stuff though - keep them coming!


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## rebel (24 Jul 2018)

Formation vs propogation vs persistence have to be carefully defined when it comes to algae. Each factor can be different.


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## HiNtZ (24 Jul 2018)

rebel said:


> Formation vs propogation vs persistence have to be carefully defined when it comes to algae. Each factor can be different.



Hopefully with enough observations we can at least build a better picture.

Is it really an algae though? There are such contradicting reports on the internet and I'm no biologist to say otherwise. Don't think the old adage "If it looks like a duck and quacks like a duck....." works too well in this instance. 

Forgot to mention that I am interested in hearing from people with GDA right now, not just those who got rid.


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## HiNtZ (15 Sep 2018)

Just to revisit this quickly, the whole no trace thing works to stop GDA immediately, but plants are clearly starving.

Really not sure what my next step it. It seems adding a little Mg causes worse problems, but adding a lot of Mg (10-15ppm) seems to alleviate the problems.


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## HiNtZ (7 Aug 2019)

Sorry to dig my own thread up but I've been trying all sorts in the past year to solve an apparent refusal by plants to take up micronutrients effectively whild GDA has come and gone. I really wasn't interested in sorting the GDA problem out specifically but noted changes in its behaviours if I would overdose and underdose certain elements.

I'm still pretty hooked on the idea that there is something to do with magnesium in the grand scheme of things. Not Ca:Mg ratios but magnesium on its own.

It seems the lower the concentration of Mg the quicker GDA appears. The higher the concentration and the growth is delayed.

Annoyingly, increased levels of Mg to prevent GDA seems to be causing stunting in my plants while underdosing it makes them turn white despite normal/heavy trace dosing - albeit understandably due to the relationship with Fe.

Perhaps the elevated levels of Mg needs to be countered with higher levels of K?

Anyone else got anything to add since we last discussed?


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## Zeus. (7 Aug 2019)

I still get the GDA on my glass which needs a weekly clean, but as long as its not on the plants I just accept it. Got a little myself on some off my anubius ATM but I'm reducing my LCO2 dose ATM which might explain it but nothing I'm concerned about.


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## HiNtZ (22 Dec 2019)

Just to resurrect this thread for an updated observation....

During these problems, whether I had GDA or not, I rarely had pearling. I know that's not an indication of anything substantial besides the fact the water is saturated with O2. It was actually a helpful thing though as visually, more traces equaled pearling and normal dose didn't. Anecdotal at best but maybe there's something there still?

Lately I've changed my water recipe. I now reconstitute with CaCO3, MgSO4, CaCl2 which gives me about 6GH/6KH (50ppm Ca, 8ppm Mg, 20ppm Cl and whatever S goes along with the Mg, 10ppm I think) - this water starts pretty clean so I know there's nothing else there that will throw me off the trail.

At the same time I trebled traces (APF trace mix EDTA) and halved macros from EI levels somewhat counter intuitively but have noticed improvements, mainly in baby tears which I've never had luck with. Went nice green and started running.

So I done a couple weeks reverting back to EI levels and again, ran into plant health problems and GDA. So the next month or so will be sticking to the new regimen. Half macro, treble micro.

This is around 1.8ppm Fe a week which seems a bit excessive but that's what it seems to want. Maybe the chelator? I did buy some DTPA Fe 7% to supplement a normal EI dose and still wasn't having much luck. I suppose the tank wants more of everything rather than Fe?

Ah well, we'll see!

Happy Christmas!

p.s Are you actually using LCO2? Or glute?


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## HiNtZ (22 Dec 2019)

Just to add, when I was running the purer water recipe (3GH/1-2KH) the EI dose seems even less effective. As if the super clean water changes were stripping whatever the last week left and the plants were always lagging behind trying to catch up to the dose.

Was always under the impression, the softer the water, the leaner the dose should be. This seems  true with macros but not micros.

I remember seeing a site selling fertiliser, micros specifically - it said "in soft water, double the dose" with no explanation why. Again, this is contradictory to "the harder the water, the heavier the dose should be".

It's definitely a strange one.


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## Zeus. (22 Dec 2019)

HiNtZ said:


> Just to add, when I was running the purer water recipe (3GH/1-2KH) the EI dose seems even less effective. As if the super clean water changes were stripping whatever the last week left and the plants were always lagging behind trying to catch up to the dose.
> 
> Was always under the impression, the softer the water, the leaner the dose should be. This seems  true with macros but not micros.
> 
> ...



May something to do with all the minerals being removed with softer water - Then maybe theres an optimum window of water softness for plants to thrive optimally ! (makes sense really)


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## JohnC (8 Feb 2020)

Hi man,

Any updates with your journey through this? I'm coming back to the forum to detail my issues with GDA on multiple tanks and found your thread. I'm a bit short of time to fully go into it now but i'm also coming from a spring water remineralised angle. I'd also been massively overdoing MG, then reducing MG, having GH high/KH zero errors over the last 6 months. 7 odd tanks with varying fert and light regimes. 

I'd also say i've had stuff that looked like micro deficiency when i shouldn't be having it. My head is somewhat being done in after chasing issues for a long while now.

Do you have any diatom issues in mature tanks too?

Cheers,
John


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