# Green spot algae- how to elminate it



## aquasox (Sep 11, 2005)

I need some help reducing/elminating GSA from my tank. Its a problem on the glass and anubia, java fern, and hair grass (not much of a prob on fast growing stems).

Tank specs:

3.6 Wpg PC lighting
pH 6.10
kH 2.20
gH 4.5

Dosing regime is EI: 

1/4 tsp KH2PO4, 1/4 tsp K2SO4, 3/4 tsp KNO3 Sun,Tues,Thurs.
1/4 tsp Traces elements on days not listed above.
10 ppm CaCl2 weekly at 50% water change.

Fish load (44 cardinals, 3 SAES, 6 scissor tail rasboras, 12 japonica shrimp, 10 ottos)


Should I add more or less PO4? Should I cut back or add any other macros?
Thanks


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## trenac (Jul 16, 2004)

GSA is usually caused by a lack of P04. Try upping the dosage and it should go away in a few weeks.


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## aquasox (Sep 11, 2005)

I've increased phosphate to 1.5 X dosing.

Could I increase it even more so its in a 1:1 ratio with NO3?

There seems to be a bit of a reduction in GSA growth so far.


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## eklikewhoa (Jul 24, 2006)

What size tank do you have?

I had a bit of GSA in my tank and I lowered the photoperiod by an hour and it seem to help a bit. My next attempt is to up my fert regime as well.


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## aquasox (Sep 11, 2005)

Tank size is 72 gallons. I have two compact flurorescent fixtures (2X65 W each). One on the front is on for 8 hours, the back one is on for 12. I could try lowering each one by an hour.


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## apistaeasy (Jul 16, 2004)

GSA is usually a sign of phosphate deficiency, but you are dosing almost 4 ppm every other day! Your phosphate levels are probably very high. 

I would guess that you actually don't have GSA, but GDA instead.

I suggest cutting back on your phosphate levels, increasing your K levels, decreasing NO3 a little, and decreasing your photo period is a great idea too.


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## aquasox (Sep 11, 2005)

apistaeasy said:


> GSA is usually a sign of phosphate deficiency, but you are dosing almost 4 ppm every other day! Your phosphate levels are probably very high.
> 
> I would guess that you actually don't have GSA, but GDA instead.
> 
> I suggest cutting back on your phosphate levels, increasing your K levels, decreasing NO3 a little, and decreasing your photo period is a great idea too.


Its definitely green spot algae. Its in round small spots and difficult to scrape off the glass. I've had green dust too, but that is easy to scrape off and forms a film over the entire glass...I've never found it on my plants like GSA.

What would you suggest increasing K too? I'm already dosing 1/4 tsp K2SO4 in addition to the 3/4 KNO3. Maybe cut KNO3 to 1/2 tsp and double K2SO4?


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## Avalon (Mar 7, 2005)

Wow, you've got plenty of PO4. Try increasing the CO2 a little bit. GSA is either CO2 or PO4 deficiency. Everything else looks ok.


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## aquasox (Sep 11, 2005)

Avalon said:


> Wow, you've got plenty of PO4. Try increasing the CO2 a little bit. GSA is either CO2 or PO4 deficiency. Everything else looks ok.


Sure I'll increase CO2....I'm getting a more efficient reactor soon too. I think the pH probe I have might have been off a little bit....time to replace.

Anyways I think we've pretty much eliminated po4 deficiency from the picture


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## hoppycalif (Apr 7, 2005)

I'm not really obsessed with drop checkers, but.....either make or buy one and use it with distilled water having a KH of 4dKH, and you can be sure what your CO2 level is. There isn't any other good way.


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## erijnal (Apr 5, 2006)

If you want a quick way to eliminate the GSA off your anubias, a dip in about a 20% excel solution will do the trick. Anubias are tough enough that there should be no adverse effects


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## aquasox (Sep 11, 2005)

erijnal said:


> If you want a quick way to eliminate the GSA off your anubias, a dip in about a 20% excel solution will do the trick. Anubias are tough enough that there should be no adverse effects


Thanks for the tip. Can you spot treat with a syringe too?


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## apistaeasy (Jul 16, 2004)

aquasox said:


> What would you suggest increasing K too? I'm already dosing 1/4 tsp K2SO4 in addition to the 3/4 KNO3. Maybe cut KNO3 to 1/2 tsp and double K2SO4?


Download the fert. calculator from this link and find out for yourself.
Chuck's calculator


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## Freemann (Mar 19, 2004)

Well I get GSA with high PO4, high CO2 all the time.


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## Avalon (Mar 7, 2005)

Freemann said:


> Well I get GSA with high PO4, high CO2 all the time.


There's always got to be _that one_ person... 

Try upping your nitrates a bit?


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## dapellegrini (Jan 18, 2007)

I was thinking of posting a very similar thread. The only algae that I have any problem with is also GSA. I maintain high CO2 and high PO4, and this does not seem to change much. Next step is to reduce my photo period and lighting intensity. I am also considering going to RO water. I know in Reef tanks, certain trace elements in tap water can also cause algae and am starting to wonder if it isn't something in the water...

Discouraging to hear that someone else is having the same problem while using less light... Errrrr... It is more of a nuisance than a problem, but one I would rather not have.

72-gallon
324-watts of T5-HO light (10 hours + 2 hours dusk/dawn @ 108-watts)
EI ferts ++
Eco-Complete
Heavily planted
Fully automated CO2 injection
-- 6dKh
-- 8.0pH out of tap, driven to 6.6 with CO2
-- NO3 ~20-30ppm
-- PO4 ~3-5ppm
-- K+ who knows, but it is dosed in with KNO3, KH2PO4 and K2SO4 every other day... I would say probably more than enough

Hmmmmmm


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## Avalon (Mar 7, 2005)

That's a lot of light for a 72! It looks like your nutrients are in order dapellegrini. I still have to point my finger at CO2 in your case. I would be curious if you were to drop your pH (/w CO2) a bit more to see if it helps.

I use 100% RO and I still got GSA. After figuring out a stable dosage of ferts as the effects of the ADA AS have mellowed out, my GSA has disappeared. I sometimes get it when the plants block the circulation in my tank. I figure that's a lack of CO2, as a little bit of hair algae pops up. As soon as I prune them back and clean the walls, GSA doesn't return.


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## dapellegrini (Jan 18, 2007)

I will bump the CO2 a bit more. In addition to my SMS122, I am also using a drop checker with a reference KH solution that I baked up some time ago. I also have some of the lab certified stuff in the mail (should be here later this week).

I just recently (in the last 4 weeks) changed out my flourite with Eco, so some of the recent issue may have to do with the change. I keep meaning to change my light schedule...


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## aquasox (Sep 11, 2005)

Just curious as I'm not really familiar with kH drop checkers (I've got a Salifert kH test kit)...how do they work and can anyone recommend a good one?


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## yildirim (Nov 25, 2004)

Everything regarding the GSA is said along this posts. Yes the main reason for GSA is CO2 and PO4 defficiency. Lighting period and density is not as important as the other two factors here. It is very commonly said that 1-2 ppm of PO4 is the required/target value but IMO I believe that ever specific tank must have its own specific targets. Some tanks may stop producing GSA at 2ppm of PO4 but some at 5ppm (like one of my tanks in the past), so you may increase gradualy to see the effect. Dosing quantity doesn't mean anything, the imp thing is how much present at the water column. For example I dose 3ppm daily. But when increasing PO4 you should always check the other nutrients because small changes in CO2 and PO4 may greatly effect other nutrients consumption. When trying to understand the effect you may cause on GSA, never look on the existing ones as it will take a long time for them to disappear and also dying or very old leaves (because in any tank they are most likely to have GSA on them as the surface movement/enlargement on the leaves are stopped and GSA needs still surfaces to attach to). The best observation could be done on younger anubias leaves.


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## dapellegrini (Jan 18, 2007)

aquasox - There are a couple different kinds of drop checkers on the market. I am using one that looks like this:










These have been around for quite some time now. The idea is to put some tank water in there along with some PH test regent to measure your CO2. The CO2 passes across the air gap and equalizes with the small test solution over an hour's time or so.

Accuracy is compromised because of fluctuations in PH and KH due to other chemicals in the water, but it gives you a pretty good idea. By using a reference solution (instead of tank water) in the Drop Checker it becomes very accurate. The reference solution is calibrated to a very specific PH/KH, giving you an accurate measure of the CO2 in your tank.

Of course I already have a PH probe, but I find this little device very useful. Last time my tank went empty, it was my drop checker that clued me in (I am not always under the tank looking at the pH meter). It is also a good cross-check against my pH probe which has a tendency to get a little out of whack from time to time.

yildirim - I have increased my CO2 and decreased my lighting cycle to about 8 hours of full-on lighting. I will see if this helps. I have maintained PO4 levels to the point that my fish started to swim funny (6+ ppm), without ridding myself of GSA... Hopefully it is my CO2 measurement that has been off a bit...


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## aquasox (Sep 11, 2005)

Thanks dapellgrini:

I too have a pH probe, but I'm thinking of giving the drop checker a shot.


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## furballi (Feb 2, 2007)

Very bright light always generate GSA on slow-growing leaves in my tank. Having taller plants over the anubias to block out the light is an excellent way to eliminate GSA on the anubias. 

Excessive feeding (fish poop is high in N and P) will also trigger GSA. That's why I'm not sure why high phosphate in the water column (above 1 ppm) would help to remove GSA. It is very rare to see GSA in a low to medium lit tank with a light fish load.


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