# phosphate and GSA



## Glaucus (Oct 11, 2009)

How are high phosphate levels > 1.5 ppm working out for you in combatting GSA? I ask this because im starting to seriously doubt the correlation between low phosphate and GSA growth. In my case i kept the phosphate levels to a modest 0.2-0.5 ppm. This went well for a long time until gradually more GSA showed up. So i raised phosphate to the for GSA supposedly inhibitory concentration of > 2.0 ppm. I monitored it for about a month, waiting for anubias barteri to produce a new leave. To my great dismay this fresh leave was overtaken by GSA at an incredible (and never before seen) pace, less than a week. 

I should note that my co2 drop checker is green. Co2 is a stable as can be (ph controlled, no night shut off). Besides upping PO4 there is one more element that i variated during this month. KNO3. I saw some nitrogen deficiencies in my tank so i decided to start dosing a little KNO3. I didn't need to dose KNO3 before with the AquaSoil leaching nitrogen. Levels were relatively high but became lesser and lesser to the point that Nitrogen was limiting. With the dosing no longer. This could have made conditions better for GSA. With both N and P non-limiting it looks like condtions are perfect for GSA and its starting to bloom.

I'm thinking of bringing back the phosphate dosis to the levels they were <0.5ppm. I won't touch the KNO3 dosing since its visually needed for the plants and used to be present at higher levels before anyway, with little problems. I would like to know from you, did upping po4 levels work out for you or did it not? Did you do anything else to worsen conditions for GSA?


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## NeonFlux (May 15, 2008)

Hi Glaucus, I usually get GSA from having a sunny window near my tank. Also during low CO2 levels, unbalanced lighting, etc. Sounds like your co2 levels are okay. What about your lighting? How long do you keep your lights on?


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## Glaucus (Oct 11, 2009)

Hi NeonFlux. The tank is placed in a somewhat bright room but never receives any direct sunlight. The lights i use for this 65 gal tank are 2xT5 with reflectors. So intensity is not that high (though enough to grow glossostigma elatinoides and hemianthus callitrichoides).

I have the lights on at 100% intensity for 8 hours. At midday there is a 2.5 hour blackout. In addition light intensity gradually increases or decreases, before or after a peak is reached respectively. For example it takes about 2.5 hour before the first peak is reached. During this time light intensity is variable between 0 - 100%. Because i use an afternoon dip, i use four such periods.

hours [intensity%]
2.5 [0-100] variable
3 [100]
0.5 [100-0] v
2.5 [0] blackout
0.5 [0-100] v
5 [100]
2.5 [100-0] v

While the light are on for 16.5 hours! Light is really dim when intensity is at <60%. So I reckon the variable light periods adds about 2 hours of effective light to the photoperiod. In total probably a 10 hour photoperiod.

EDIT: im looking into the option of noon-burst as opposed to siesta right now. I found an interesting read over here:
1. http://www.plantedtank.net/forums/algae/56231-green-spot-algae-treatment-suggestions-2.html
2. http://www.barrreport.com/showthread.php/4916-Optimum-Light-Period/page3
3. http://www.aquaticplantcentral.com/beta/lighting/44768-current-thoughts-noon-burst-noon-siesta.html

Quote from [1]


> Based on the mixed input I am receiving here, I am going to try a little compromise and test. I am going to set the tubes on two seperate timers to mimick "noonburst." Right now I am running split photoperiod of 8 hours total and it not working with the GSA. I will set one bulb to burn for a total of 4 hours, then will set the other bulb to come on after 4 hours. [...] FWIW, the only change I made the tank was a switch to 8 hour noonburst photoperiod and the Green Spot Algae has myteriously vanished as quickly as it appeared. I tried split 8 hour photoperiod but plant growth was being negatively effected(funny considering that plants in another tank are still growing like weeds with 8.5 hour split - 2 hour siesta).
> 
> So, with no other changes made to the tank, I think it is safe to conclude that at least in my case that either noonburst photoperiod did the trick or the tank just balanced itself over time which would have happened without the switch to noonburst.


Quote from [2]


> I too had algae issues when I did two 5 hour periods (6-11am and then 5-10pm). I had read (though not sure if it's proven) that while algae gets up and going very quickly after lights come on that the higher plants take longer to get their "engines revved up" and to take advantage of the lighting. Therefore it would seem a broken up lighting period would favor algae and a longer single light period while not exactly favoring either would allow plants to grow better and have more success in out-competing the algae.
> 
> I went to a single 8 hour period (2-10pm) and most of my algae issues practically disappeared (GSA, BBA). I also notice that the biggest pearling of my plants does not start until about 6pm and things are pearling like mad by 8 or 9pm. So it would appear that the strongest growth and pearling may be happening 4-6 hours after the lights have been on. If I'm doing short periods of 4-5 hours then I hardly or never even get to that point.


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## NeonFlux (May 15, 2008)

I have afternoon bursts timed for my 3x54 T5 lighting. 2 hr 54w plant grow, 4 hr all 3 54w lights, then 2 hr plant grow. I used to get GSA, but that was because I had my co2 levels and nutrient levels out of sync... eventually I fixed co2 and nutrient levels, and etc everything went GSA-less after removing them manually. I am not certain now the cause for GSA in your tank. Perhaps with all the change in photo periods, it could be affecting your tank somehow..


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## Glaucus (Oct 11, 2009)

Hey NeonFlux. Can you tell me more about the desync problem, too much Po4 and limiting Co2 perhaps? What went amiss? And what is your current dosing regime. What Macro levels are you targeting, esp. po4, nitrogen? BTW i now changed the light scheme to a 5 x /wk noon burst 2 x/wk siesta. Everyone likes a siesta right? :fish2: Gotta have one of those. On a serious note, i will eventually phase out the siesta completely.


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## NursePlaty (Mar 24, 2010)

I had the same problem here and I never dosed KH2PO4 anymore bc I did not want my phosphate levels to rise. I talked to Tom Barr and he said the phosphate was not the problem and he maintains his at 3ppm with no algae issues.

I have 2 tanks, 1 with gsa and 1 without gsa. The tank WITH gsa has low lights that are not on a timer and has no ferts. The tank WITHOUT gsa has high lights on a timer with ferts. Phosphate level is also really high, maybe in the 4-5ppm. The only algae in that tank is cladophora. Maybe gsa has something to do with the light, like a fluctuating photoperiod. Or maybe ferts.


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## Glaucus (Oct 11, 2009)

So.... after a while of change from siesta too noonburst, things more or less remained the same perhaps became slightly better. The real change almost happened overnight this weekend. I did a major water change and now a couple of days later a severe GSA outbreak became fact. Not only was Anubias colonized by green spots but this time some of the java fern leaves as well which always remained untouched. I have never seen it take over this quickly (my previous GSA record definitely broken). What actually changed with the water change? Well the Nitrate levels in the tapwater are a steady 15 ppm. I kept No3 in my tank at a low 3 ppm before the major water change. So, No3 went up quite significantly, as did Ca and MG, K went down, Po4 remained steady, Co2 went up. Too me this indicates that sudden change in No3 pushed the GSA to the next level. Thus again, the high Po4 and co2 levels could not help to prevent this outbreak. Perhaps the GSA will slow down after a new balance has been established in the tank with higher than usual No3 levels. I guess i'll have to wait and see.


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## Glaucus (Oct 11, 2009)

The GSA outbreak has been solved, for now. I cut away the infected leaves, lowered No3 levels to the point where the ratio N was 3:1. New growth remains clear. I'm not sure if the ratio has anything to do with solving the issue or that it was a coincidence. I have changed multiple things at once. Anyway it is a ratio that makes sense when using a Po4 base of 2.5 in a GSA context. It shows up here and there as a beneficial ratio.


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