All,

I have two tanks. A 29 gallon with injected CO2 and a 10 gallon using Excel. The 10 gallon is ALWAYS in better shape and nicer looking because the 29 gallon has been plagued by green spot algae. This is the only algae that I ever seem to run into with this tank. It appears to occur whenever I trim the plants. The trimmed plants will have GSA on a few of the leaves just below where the trimming occurred. The GSA is also prevalent on my micro swords which cover the foreground. Why does it appear consistently on the leaves below the trimmed point?

Light = 65 W of PC. It is on two 65W bulbs that switch half-way through the day.

Ferts
3x a Week = 5ml Tropica Master Grow; 1/4 tsp KNO3; 1/16 tsp Mono Potassium Phosphate;
Daily = 5ml Excel.
1x a Week = 1/8 tsp Potassium Sulfate; 1/4 tsp Magensium Sulfate; 1/2 tsp Calcium Sulfate.

CO2
Compressed. Drop Checker at a light green with 4 deg. KH solution.
I run the CO2 line into a RIO 180 to chop up the bubbles. The air intake of the RIO is also re-routed into the impeller.

Circulation
1 RIO 180 for CO2. Another for additional circulation. (2 x 120 gph)
FLUVAL 205 (180 gph) hooked into a Spray-bar.

Any comments / suggestions are appreciated. When I do a water change half-way through the light cycle the plants pearl intensely. I only notice moderate pearling during the day w/o water changes.

Why do you let the powerhead suck air into the water flow? Air will not help with CO2 injection. Did you use distilled or deionized water for the drop checker?

I am not pulling air into the power head. I mean to say that where the air intake (ventrri nozzle?) would be I routed that back into the impeller. I figure this would allow a bit more CO2 to enter solution in the water. So, the only gas going into the power head is CO2.

I used distilled water in the drop-checker.

When I had a 29 gallon I ended up dosing about halfway between 1/16th and 1/8th tsp of KH2PO4, in order to prevent green spot algae. So, you might try that. From your description it seems like low CO2, but the drop checker seems to be saying you have 30 ppm or so, which should be right. Now I understand how you hooked up the powerhead, so that seems all right too.

Do you dose KH2PO4 the same time you dose the trace element mix? If so, you might be precipitating out the iron and some of the phosphate.

I'd still focus more on CO2, if the PO4 is up as well, you should not have GSA issues.

If you get GSA or any algae after a trim etc, do a large water change right after the trim or any work inside the tank as a rule.

also, when you change the water, make sure the drop checker is changed at least once every week or two, keep up on that also and realize..it's got a 2-4 hour delay in color resolution.

So some tweaking with your eyes and watching the plants,, should help.

Regards,
Tom Barr

I have been doing 1/16th of a tsp 3x a week on alternative days from the micro nutrients. So, I don't think the combination with iron should be an issue. My tap water comes out at ~ 2.0 ppm, so I am thinking 1/16th tsp should be just fine.

I will look into the CO2 more thoroughly. I have not been changing the drop checker solution bi-weekly as suggested. Also, the lights/CO2 kick in while I am at work. I note a YELLOW color when I get home. Perhaps, the 30ppm of CO2 is taking longer to establish in the tank. I will see about having the CO2 kick in a little earlier or alternating my diffusion methods.

Thanks.

I'd just check the CO2 good.
Sounds like the rest is okay.

GSA is a PITA and I'm glad I no longer have to deal with it.
Still, it's a two cause algae.
CO2 and PO4.

I think there might be another method also to get rid of it over the longer term also.
But the above does work over a wide range too.


Regards,
Tom Barr

When you state PO4 as a cause, you specifically mean a lack (or low enough to inhibit growth) of PO4 correct?

What is the other method you are eluding to? I know when it is on the glass you can wait a few weeks and then clean it off. Is there another method for it when it appears on plants?

Green spot algae and green dust algae are completely different. It is GDA that can be allowed to live out its natural life cycle before cleaning it off the glass. GSA forms small circlular spots on the glass and leaves, which grow to much larger sizes. Those need to be scraped off the glass, and if the amount of phosphate dosage is increased it will often stop it from coming back. I'm curious about the other method too? A blow torch???

Another question in relation to this...

The GSA looks to be dead sometime after it appears. It turns a very dark green, maybe even a black color after some time. If it is in fact dead, will it eventually fall off of the leaves? I tried to rub it off with my fingers but it persists. I am wondering if I am stuck with the algae on the leaves it has formed on. Is my only alternative to uproot and replant the plant tops?