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Discussion Starter · #1 · (Edited)
Hello, my name is Otavio and I'm from Brazil. I have been experiencing this alga for a long time and I may not be able to identify it.
It looks a lot like GDA, I run my fingers over the plants and get out very easily

I lost my carpet from Micranthemum sp. Monte Carlo because of that seaweed. :confused:


I fertilize my aquarium with N, P, K, FE, Flourish, Flourish Advanced e glutaraldeído or “commercial ”liquid carbon."

Seachem Equilibrium e KH Booster Microbelift

I try to keep my parameters in:

Tank: 180 liters or 47 gallon
PH: 6,8
N: 10ppm
P: 1pmm
GH: 6
KH: 7

I suspect it is a problem related to my CO². I increased the flow a little to see if it resolved and nothing happened.
I will attach a video of how it is working.

I use a WRGB 90 Chihiros lamp with 8 hours a day.
6 hours at 100% brightness and 2 hours waking and sleeping. 1 at the beginning and another at the end of the photoperiod.


Anyway, this is the only seaweed that is irritating me and I don't know what to do anymore. If anyone has any suggestions I will be very grateful.



528 Posts
The resolution of your pictures makes it a little difficult to see what it is. If it removes easily it's probably not a variety of Green Spot Algae (GSA) which is difficult to remove. GDA can look like what you have and typically removes very easy, even kind of powders in the water when you wipe it. It could also be cyanobacteria although that will look a little more blue greenish, will feel slimy, and can have a fishy smell when removed from water. That's a more serious issue.

GDA seems common in new tanks, before cycling, and/or before plants take hold and remove enough nitrates from the water. Your nutrient levels are pretty lean at 10N/1P. You can try a higher concentration to see if that has an effect, it will make many plants grow faster. Your tank is somewhat sparse to medium planted so you should not need to add high doses on a regular basis.

It has worked for me with algae to turn the lights down a little (and fewer nutrients as a result of less photosynthesis) to get it under control and then gradually bring them back up. However your light cycle seems modest at just 6 hrs full. But I don't know how bright your lights are, it could still be too much. If you are in the "high light" category during that 6 hours, you could try cutting it back a little, maybe doing more of a taper with 2-3hrs at full, then gradually up/down on the shoulder hrs.

Physically remove algae where ever you can as that makes it easier to see if it is growing back or not. It's harder to tell when there is already algae on everything. As well, algae begets more algae. If it floats up into the water column when you touch it, use a Python or siphon tool to suction it out as you manually clean off the plants.

Moderate/heavy water change regimen seem to help, like 50% per week. I think they work to keep organic wastes and other nutrients that algae may feed on in low supply. I have similar size (50g) tank to yours. I have shrimp and don't like to cause them to molt, so I do small changes @10% per day, or basically replace a 5 gallon hardware store bucket full each day. 1 bucket a day makes it easy and fast.

Any changes you make will take a while for results so you have to hang in there. Don't make too many changes at once so you'll have a better idea what is working and what isn't.
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