Green Spot Algae Issue.

Gorillastomp

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Dec 26, 2020
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Hey guys,

I have an issue with recurring GSA in my 240 Gal planted tanks. It's seems i can't figure this out. I started the tank in september 2020 and had no algae for about 2 months then thing started to change when i had to change my lighting setup + introducing the livestock.

I passed from diatoms To some BBA then GSA. Fixed the BBA issue by increasing my flow/co2. But now i have GSA everywhere, on old plant leaves, rocks, wood and glass.

Lets start with the fishtank stats :

Temp : 28c or 82 F (Discus Tank)

Light up for 7 hours (2 hours ramping at start and end included in the 7hours)

No3 : ~10ppm

Po2 : ~ 1 ppm

Fe : ~1 ppm

Dose everyday with automatic dosing pump :

KNO3
KH2PO4
K2SO4
CSM+B
Excel

Water Change of about 70% every 3 days.

Co2 : Ph at 6,5 From a degassed ph of 7.9

KH : ~ 3,5 or 80 ppm

GH : ~ 5 or 120 ppm

What i tried so Far :

+ Did an overdoes of Excel, it worked but algae came back after 3 weeks.
+ Lowered light intensity
+ lowered light up time
+ increased Co2
+ increased Po2 at 5 ppm

Always let the changes sit for at least 2 weeks between each of them.

Now i am a bit lost on what should i do now ?

PS. I have seen the timeframe of the S.repens growth from Tom Barr past tank. Mine never grown quick like that. So i know there is something wrong but i can't point it out.
 

Allwissend

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1 ppm PO4 is per dose (7 ppm PO4 per week ?)? or per week ? or the measured aquarium concentration ?

Increasing PO4 will usually reduce the growth rate of this algae. The existing algae will have to be manually removed. With enough time at high PO4 levels the algae is not a problem.
 

Gorillastomp

New Member
Dec 26, 2020
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Canada,Quebec
These are the concentrations in the water column prior the water change.

At the moment i dose around 1 ppm worth of PO4 weekly + fish feeding.

Used to have my PO4 concentration at 5ppm + and GSA was still growing.

I was referencing to my water test kit, maybe it is misleading me. I'll make a reference solution to see if it is accurate.

For now i will triple my dose of KH2PO4 and see what is going furing the next weeks.
 

Allwissend

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Sometimes algae just want to show how adaptable they are, but on average higher PO4 (3ppm+) seems to have at least slowed them down for me.