Algae that doesn't fit any existing description



Hi everyone,

I'm setting up a new tank (just over 1 month old), and have been fighting this algae that I'm not really sure if it is blue green algae or green dust algae. I've been reading up a lot but it doesn't seem to completely fit any descriptions I found online.

It first appears on glass as green dots or blobs. It's not like green dot algae which is supposed to be hard, but soft blobs that flutters in the water current. After a while they appear on rocks and plants, growing bigger blobs, and I can see them photosynthesizing, making oxygen(?) bubbles.

When they appeared the first time, I thought they were BGA (as new tank had 0ppm NO3). I did a 3 day blackout which seemed to get rid of them and fixed to 0 NO3 issues. A week later they are back.

Not sure if it is GDA (as it goes everywhere not just glass). Not sure if it is BGA (as it's not blue, and are blobs and not sheets). Please see photos below. I wonder if someone would be able to tell what they are? That would be very much appreciated.

Tank is 200L (60gal), dosing EI, current parameters

- NO3 20ppm

- PO4 1ppm

- Ammonia 0.5ppm

- Nitrite 5ppm

- pH 6.4

- CO2 30ppm, pressurized (based on drop checker)

No fish yet
Last edited:

Dennis Singh

May 5, 2013
Orange County, CA
On the glass, looks like gsa. Don't know about the rock. This is good example of cycled tank after a month. You barely have any algae, thats good. With the leech people usually battle the first month like crazy. Things looking pretty good. Plants aren't best though.
Mar 20, 2013
I've had the jelly-like blobs in my tank before. No idea what it is but I got it from an incoming plant.

The condition of the plants look terrible.


Yes the plants look sick. They were growing happily until smothered by these blobs in the first attack. Blackout got rid of them (for a while) but left the grass really in bad shape.

By the way when you had these jelly blobs what do you do? Did you manage to get rid of or limit them?


Thanks for the quick replies strungout and Socielo.