Red powdery substance

[NitrateKillah]

Anyone ever had this? I have never seen this before? its not red slime, as I had and see this before.

I seen my tang try to eat it, and it turns to powder. What can this be? its reddish/orange like clumps.

 

[K7BMG]

Without pictures and a full work up on tank parameters size age and the like its impossible to answer.