Pineapple sponges? I hope

[SkylineView]

These have gone bananas in my tank over the last 6 months. My tank maintenance could have been better recently (work/kids etc), and I’m working on getting it back in order. Just want to affirm why I’m dealing with. Hoping (?) it’s just pineapple sponges?



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Grows almost everywhere except in direct light. About the size of a grain of rice. Flexible stalk, waves in the water. They’ve been around a while, so I don’t think they get any bigger.

Tank: 100 gallon, ~3 years old
Equip: skimmer (just upgraded), just added gfo/carbon
Cuc: robust
Fish: clowns, fox face, gamma etc (pretty normal stuff)

Parameters:
Ammonia near zero
Ph normal
Nitrite near zero
Nitrate elevated (pre gfo)
phosphate zero (just added gfo / carbon)

Appreciate any ideas from those who’ve been around the fish-tank block.

 

[StartingATank]

I don’t think those are pineapple sponges. I am unsure of what they are

 

[CaptainScuba]

Look like Hydroids? I don’t know the solution - I don’t think there’s an “easy” fix for them.

 

[SkylineView]

Update, I broke out the kids microscope. The arms were really active… my wife doesn’t like this guy.

 

[SkylineView]

After a bit sleuthing around, I’m 98% sure it’s hydroids. Not great. For anyone looking for a good thread on these things… see here: https://www.reef2reef.com/posts/8798589/