Anthony, another ID...Strange algae

[Caesar777]

You're always so helpful with ID's...This one has us all stuck.

Tank owner's description of the stuff:

Well, I can tell you these things for sure; very dark brown, plating, parts that grow off the rock(out into space) can be peeled off, peeled off chunks feel like slimy plastic(hard), won't come close to blowing off(won't brush off either), covers over anything like a hard sheet, grows really fast, seems to be breaking up in spots and reforming elsewhere, and generally has me concerned! I thought diatoms were kind of dusty and could be blown around. Is that wrong? By your info, it sounds like diatoms. I was at first thinking cyano, tried two doses of chemi-clean, and that had NO EFFECT AT ALL on it. The tank is about 6 months old and I've had a small bout with hair algae(I won!) and never saw anything that looked like what I thought were diatoms. Using distilled water from the start. No over-feeding. PC lights at 12 hours. This stuff just showed up about 4-6 weeks ago(about 4.5 months into it).

Thanks in advance!

 

[Anthony Calfo]

eh... an easy one I do like plants and algae.

This growth is Lobophora. I'm as certain as I can be from a pic ID.

Do some searches for that name, of course.

You will find that it can be a boon or scourge... at times getting invasive. Control by snails or herbivorous fishes is usually ineffective. Manual extaction does not spread it badly... but it is tough to remove.

I prefer to use (even if only temporarily) urchins to raze it.

 

[Caesar777]

Excellent! Thanks again!