[JHeard]

Hello to all. I have been a member for a while, but usually just peruse the threads to find what I need (with pretty good success). I have been "experimenting' with s/w for about 2 years, with my share of disappointment. It is a great hobby, but not a cheap one!

I have two tanks, a 55 gal FOWLR and a 27 gal w/ 1 fish and a little LR.

The reason I am posting now is because I have not found an answer to an ongoing "problem" (?) with my 27 gal. No matter how much I change the water, a day or so later I have this green matter that starts to cover the sand. I want to think that it is coraline b/c when I try to remove it, it is definitely solid - doesn't seem to be cyanobacteria. My 55 also has this, but not to the same degree.

My #s are:
pH 8.2
nitrates 20ppm (almost always 20 in both tanks)
temp 80 F
sp gr 1.025

IMG_2590.jpg
IMG_2592.jpg

Thank you in advance for any help/guidance!

[pogodzib]

Welcome to RB Jim! From the pics, it looks a lot like green cyanobacteria, but you said that it is hard. I've never seem green coraline algae grow like that though.

[JHeard]

Thank you for the reply. It seems like it forms a "crust" after a few days that starts to cover the sand. It has me puzzled for sure. I try to suction it up when I perform water changes, but it always starts to reappear a day or so later...

[pogodzib]

Sounds like cyano if you are able to suck it up and it reappears after a day or two.