Precipitate?

[MmmmBalf]

I have all these white stalactite shaped things forming throughout my tank and sump. They are around 5mm long, and feel squishy if you pull them off. They seem to mostly form in darkened areas - undersides of rocks and in the weir and sump.

Is this some form of precipitate? Any ideas of correcting the chemistry if it is? Should I remove it? There's heaps, especially in the sump and weir.

Current tank parameters:
Alk : 7.9 dKH
Ca : 460 ppm
Mg : 1300 ppm (that was a week ago, may be slightly higher as I've dosed a small amount during the week)

Thanks for any assistance.
Michael

 

[cjd]

Pineapple sponge, harmless good filter feeders. Only problem they can become a nuisance if they enter the display. Side note.... I have had sumps full of them and never really noticed them in the display.

 

[MmmmBalf]

Oh wow, thanks! Not at all what I was expecting. Learn something new every day