Please help identify! Salt build

[fishrfriends2025]

Been running this fluval evo 13.5 for over a year now. Could anyone help me identify what exactly this is in my back filter compartments? This whole time I’d just assumed it was salt build up but it almost looks like they have tail like structures. There always stationary though which led me to believe it was just salt build up. It vaguely looks like snail eggs from other pictures I’ve seen but I don’t really think it’s eggs since I’ve never seen them develop or anything. Any input would be greatly appreciated! Thank you!

 

[Fish Fan]

Welcome to Reef2Reef!

Are you seeing pineapple sponges, which are harmless, and thought to be a beneficial filter feeder? They literally look like a little white pineapple. This one is upside down, but they grow every which way:

 

[UncommonSense]

Been running this fluval evo 13.5 for over a year now. Could anyone help me identify what exactly this is in my back filter compartments? This whole time I’d just assumed it was salt build up but it almost looks like they have tail like structures. There always stationary though which led me to believe it was just salt build up. It vaguely looks like snail eggs from other pictures I’ve seen but I don’t really think it’s eggs since I’ve never seen them develop or anything. Any input would be greatly appreciated! Thank you!

Mini feather duster worms!
Quite common, and beneficial little filter feeders!

Edit: I think @Fish Fan has it nailed; the bodies look more round like a pineapple sponge; not like a piece of spaghetti!

 

[Fish Fan]

Here's another pic, something like what I think you're seeing. They like the dark, that's why they are growing in the filter compartment:

 

[Fish Fan]

Here's a pic I just took of one of my tanks. These are mini feather duster worms:

This is another of my tanks, a very new tank. This is a pineapple sponge that's on my main rock work, but it's there because I didn't have the tank lights running for a few months on startup. They are also growing in my dark filter section too:

 

[fishrfriends2025]

Here's another pic, something like what I think you're seeing. They like the dark, that's why they are growing in the filter compartment:

Here’s a slightly better picture. Sorry it’s hard to get a great picture with how tight the compartments are back there but I think you’re spot on! Should I be concerned with the sheer amount of them or no harm no foul? I’ve got a rock flower anemone, a Duncan, a toadstool, GSP, and Pulsing Xenia (seems like people hate pulsing xenia but I love the look of it and have been lucky in the sense that it hasn’t really spread from its original placement a year ago) along with a clownfish. Everyone’s been extremely healthy with no negative signs. Corals have been growing steadily, etc. Didn’t know if it’d do more harm than good removing what I’m know learning is sponges or if I need to address it. Really appreciate your ID on those! Was impossible for me to get a Google-able look up

 

[fishrfriends2025]

Mini feather duster worms!
Quite common, and beneficial little filter feeders!

Edit: I think @Fish Fan has it nailed; the bodies look more round like a pineapple sponge; not like a piece of spaghetti!

Thank you for your response! I couldn’t get anything close enough on Google look up to get me to solid answer I really appreciate it!

 

[tbrown]

Here's a pic I just took of one of my tanks. These are mini feather duster worms:

This is another of my tanks, a very new tank. This is a pineapple sponge that's on my main rock work, but it's there because I didn't have the tank lights running for a few months on startup. They are also growing in my dark filter section too:

I was sad my 70 didn't ever get Pineapple sponges. Plenty of the feather dusters but 0 Pineapple sponges.

 

[tbrown]

Here’s a slightly better picture. Sorry it’s hard to get a great picture with how tight the compartments are back there but I think you’re spot on! Should I be concerned with the sheer amount of them or no harm no foul? I’ve got a rock flower anemone, a Duncan, a toadstool, GSP, and Pulsing Xenia (seems like people hate pulsing xenia but I love the look of it and have been lucky in the sense that it hasn’t really spread from its original placement a year ago) along with a clownfish. Everyone’s been extremely healthy with no negative signs. Corals have been growing steadily, etc. Didn’t know if it’d do more harm than good removing what I’m know learning is sponges or if I need to address it. Really appreciate your ID on those! Was impossible for me to get a Google-able look up

They're good. They'll start self regulation.

 

[Fish Fan]

I was sad my 70 didn't ever get Pineapple sponges. Plenty of the feather dusters but 0 Pineapple sponges.

I have no idea what I did, except they must have come from some of the TBS rocks I've had for about two years now. I have them all over multiple tanks. I have the little feather dusters in one tank, but they are starting to grow everywhere.

Thanks for your help here!

 

[tbrown]

I have no idea what I did, except they must have come from some of the TBS rocks I've had for about two years now. I have them all over multiple tanks. I have the little feather dusters in one tank, but they are starting to grow everywhere.

Thanks for your help here!

Yeah, this was the first tank without them.

 

[Fish Fan]

Here’s a slightly better picture. Sorry it’s hard to get a great picture with how tight the compartments are back there but I think you’re spot on! Should I be concerned with the sheer amount of them or no harm no foul? I’ve got a rock flower anemone, a Duncan, a toadstool, GSP, and Pulsing Xenia (seems like people hate pulsing xenia but I love the look of it and have been lucky in the sense that it hasn’t really spread from its original placement a year ago) along with a clownfish. Everyone’s been extremely healthy with no negative signs. Corals have been growing steadily, etc. Didn’t know if it’d do more harm than good removing what I’m know learning is sponges or if I need to address it. Really appreciate your ID on those! Was impossible for me to get a Google-able look up

No problem, happy to help, and those really do look like pineapple sponges. As @tbrown mentioned, they self regulate, and are typically no cause for concern. A sign your tank is doing well and maturing.

Happy reefing!