What is this business in the sand?

[CharlieAsh]

What is growing in my sand bed? Happily ignore or show concern?

Bonus: Bowie and Blackie made appearances

 

[Subsea]

This tank is 25 years mature. I have the same stuff on glass below substrate. It’s part of a healthy ecosystem.

 

[CharlieAsh]

This tank is 25 years mature. I have the same stuff on glass below substrate. It’s part of a healthy ecosystem.

25 years?!? That is amazing!

 

[homer1475]

Just cyano/algae growing just below the surface. Completely normal, and nothing to freak out over. Part of having a sandbed.

 

[CharlieAsh]

Just cyano/algae growing just below the surface. Completely normal, and nothing to freak out over. Part of having a sandbed.

I thought cyano was bad? I'm very confused

 

[homer1475]

In excess anything is bad. Thats just normal.

 

[homer1475]

Do you vacuum the sandbed occasionally? Clean it up on your next vacuuming day, or leave it be.

You either clean your sandbed, and get rid of it, or you don't, and live with it. Just one of those things in reefing.

 

[Rick's Reviews]

I'm not familiar with deep sandbeds, I assume it would be the same as algae growing on glass but because it's deep and very little oxygen available for the algae it don't thrive/ grow as much underneath the sand but can sometimes appear due to direct sunlight?

 

[Subsea]

I thought cyano was bad? I'm very confused

There are numerous variety of Cynobacteria. Without Cynobacteria, Earths athmosphere would still be methane & sulfur. Some Cynobacteria live in coral biomass and convert dissolved nitrogen gas into ammonia which is a backup when nitrogen is limited as a dissolved inorganic nutrient.

Coral-associated nitrogen fixation rates and diazotrophic diversity on a nutrient-replete equatorial reef - The ISME Journal

The role of diazotrophs in coral physiology and reef biogeochemistry remains poorly understood, in part because N2 fixation rates and diazotrophic community composition have only been jointly analyzed in the tissue of one tropical coral species. We performed field-based 15N2 tracer incubations...

www.nature.com

“The role of diazotrophs in coral physiology and reef biogeochemistry remains poorly understood, in part because N2 fixation rates and diazotrophic community composition have only been jointly analyzed in the tissue of one tropical coral species. We performed field-based 15N2tracer incubations during nutrient-replete conditions to measure diazotroph-derived nitrogen (DDN) assimilation into three species of scleractinian coral (Pocillopora acuta, Goniopora columna, Platygyra sinensis). Using multi-marker metabarcoding (16S rRNA, nifH, 18S rRNA), we analyzed DNA- and RNA-based communities in coral tissue and skeleton. Despite low N2 fixation rates, DDN assimilation supplied up to 6% of the holobiont’s N demand. Active coral-associated diazotrophs were chiefly Cluster I (aerobes or facultative anaerobes), suggesting that oxygen may control coral-associated diazotrophy. Highest N2 fixation rates were observed in the endolithic community (0.20 µg N cm−2 per day). While the diazotrophic community was similar between the tissue and skeleton, RNANA ratios indicate potential differences in relative diazotrophic activity between these compartments. In Pocillopora, DDN was found in endolithic, host, and symbiont compartments, while diazotrophic nifH sequences were only observed in the endolithic layer, suggesting a possible DDN exchange between the endolithic community and the overlying coral tissue. Our findings demonstrate that coral-associated diazotrophy is significant, even in nutrient-rich waters, and suggest that endolithic microbes are major contributors to coral nitrogen cycling on reefs.”