alge

[Firstman]

I have marron alge forming I wonder if this is good or bad it is tipically on my sand. and spreading rapidly

[Mr Cob]

I have marron alge forming I wonder if this is good or bad it is tipically on my sand. and spreading rapidly

If it's a new tank it's expected and lasts about a month. Adding a refugium with macro algae helps.

Give more tank details if it's not a new tank.

[Iplantz]

Try looking up Diatoms or Cyano.