White squsihy sacks...almost look like cotton balls...

[BaylorbearSW]

???

They are on the underside of most my rockwork and got quite a few of them...

 

[whippetguy]

sponges, not harmful at all. The whites do tend to grow on the underside of the rocks out of the light.

 

[SaltyChick]

+1 on the sponge

 

[BaylorbearSW]

Are these generally a sign of good, bad, or indifferent water quality?

 

[engineer goby]

indifferent

 

[Doogle]

On a different note i would try to pull out as much of that bubble algae as possible.

 

[David Shaw]

On a different note i would try to pull out as much of that bubble algae as possible.

+1

 

[Conway Corals]

And try not to pop them, otherwise it will spread everywhere.

 

[taunt406]

Yep looks like a sponge to me, lol funny that they come in on almost all the live rock I buy.

 

[dmatt88]

Q tip sponges. Harmless filter feeders.

.............its calibrate ur hydrometer month. no not really but Sheez its important.