help to ident.

[workn2hard2day]

Not sure what this is. Has started to grow all over. I think it's most likely bad, but not sure what to do about it.
http://i84.photobucket.com/albums/k38/WORKN2HARD2DAY/tank001.jpghttp://i84.photobucket.com/albums/k38/WORKN2HARD2DAY/tank002.jpghttp://i84.photobucket.com/albums/k38/WORKN2HARD2DAY/tank006.jpg
All advice appreciated.

[mark]

looks like some nice sponge

[christyf5]

Good stuff, although it can be annoying if it takes over. A side benefit is that it holds your rockwork together! :biggrin: