Rust Colour?

[binman]

strange rusty colour over sand and shells in tank anyone know what this is? good or bad?

 

[SkiFletch]

Ummm, either diatoms or cyanobacteria... The first rather begnin, the second pretty nefarious.

 

[kkyyllee]

sounds like the start of cyano, or if ur tnaks new then diatoms

cyano is a pita...