Looks like a BLACK PEARL

[DaisyPolyp]

Ok, here is a tough one:

I have had my LR for about 4 months, but I have seen this in 2 places at opposite ends of my tank. To the naked eye they look like a "gun steele" ball berring, but they are not hard. They have stayed like this for at least 3 weeks with no sign of growth or change. I have not seen anything like this in any of the other posts or FAQs out there. PLEASE HELP ID!

(for scale there is a baby snail in the bottom left corner)

 

[DaisyPolyp]

The other one:

 

[investigator1]

It is a macro algae commonly referred as,
"bubble algae".

 

[Anonymous]

Valonia

 

[Anonymous]

yep, valonia. don't pop it!

 

[DaisyPolyp]

Is it something I want to have, or is it a pest?

 

[WannaBeReefer]

Considered a pest, problem is if you break the bubble it spreads and spreads.

 

[Anonymous]

emerald crabs will take care of these, if you are the type of aquarist who is not anti-crab.

 

[tenshi]

I tried emerald crabs about 4 or 5 months ago. The emerald crabs past away and they never ate any of the buble algae! I try to pick as much as I can without popping them. I think I'll do that today.

 

[Anonymous]

If you have a siphone hose that's large enough to suck up the valonia balls, use a tweezers or your fingers or something to scrape them off the rock and immediatly siphon them out. bamf!

 

[John_Brandt]

This may not be Valonia. Glassy, "bubble algae" fits the description of several genera as well as a particular stage in the development of some filament algae.