GSA getting under my skin

Carissa

Guru Class Expert
Jun 8, 2007
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Hi,
My established 10g tank which I have been doing ei on for months with 50% water changes weekly, has decided to have a spell of gsa. I didn't think much of it for a while because it was slow growing but it's really not going away. I tried doubling phosphate, leaving out phosphate, and increasing the rest of the ferts, over a period of about 3 weeks, and nothing seems to be doing anything about it. It just grows right back although a really good scrape keeps it down for a week or so. It started when I was doing co2 and lately I've been having issues with co2 production but seeing as how it began when my co2 was good, I don't think that's the cause. My oto's don't seem to be eating it either. It's mostly on the glass. Plants are all really healthy and growing well. It smells like strong cooked greens when I scrape it off. Any ideas? I have 20w of light on this tank for about 7 hours a day (used to be more but I cut back when I started seeing the algae but again that hasn't had much effect).
 

Gerryd

Plant Guru Team
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Sep 23, 2007
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Hi,

If GSA means green slime algae, I had a problem with this and the problem was too much c02. I cut the c02 down by 2/3 of what it was, and within a few days it was gone.

Won't guarantee this is the problem, but is worth looking at.
 

ceg4048

Lifetime Charter Member
Lifetime Member
Mar 21, 2005
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Hi,
It's generally agreed that Green Spot Algae is induced by either low PO4, low/unstable CO2, or both. I can't imagine that lowering the CO2 concentration can do the plants any good at all. You normally want this value to be as high as possible (without stressing fauna) and to be as consistent as possible. Therefore I would hesitate to suggest CO2 reduction as a cure for any algae, including slime. There are so many variables in the tank that one has to be careful to avoid drawing conclusions based on circumstantial evidence alone. I doubt seriously that you could induce slime or spot algae by increasing stable CO2 levels by 2/3rds but you might be able to induce it by continually varying the levels. The disappearance of the slime algae was most likely cause by some other factor which occurred coincident with the reduction of CO2.

Deleting PO4 is always an extraordinarily bad idea as this can result in stunted growth and other algae problems. It would have been better to increase all nutrients for that three week period. Then, work on stabilizing the CO2 using a drop checker with 4dkH water to monitor the levels. DIY CO2 is notorious for it's instability, but it could also be that there are problems with the regulator, the diffuser or with circulation.

Cheers,
 

Carissa

Guru Class Expert
Jun 8, 2007
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Sorry, I meant green spot algae. Should have been more specific. I know reducing co2 is not good but lately I seem to have had no choice. Since it started before I was having problems with co2 I figured there must be some other issue causing the problem although low co2 doesn't help any.
 

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
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DIY CO2 is often the Achilles Heel for algae.

Also, the time difference between algae appearance and environmental stress are not the same. It might be 1 week prior or two etc.

Unless you are measuring and testing, eyeballing/guessing does not cut it.
You have to confirm and induce to see such patterns.
Hobbyist virtually never do this step and end up believing all sorts of things as a result.



Regards,
Tom Barr
 

Carissa

Guru Class Expert
Jun 8, 2007
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So would it be better for me to stop doing co2 at all, or to have fluctuating levels? What else could be causing the spot algae?