The great hydroid debate

[Jamie9]

I've got a few of what I am assuming are hydroids on my live rock from TBS, in my quite new 40G tank (details in my tank thread if anyone wants more info on what I've got going) In my research, I'm finding it seems like not a whole lot is known about these things, other than that some people have had bad experiences with them spreading and stinging and otherwise causing damage...and some people have had them for years with no issues. I've included a couple photos below, I'm referring to the translucent tentacle-like shapes growing off the live rock. My personal inclination so far is to just let them be, I love the idea of diversity in my tank, and at least at the moment they are inhabiting islands of life in an otherwise new and fairly barren tank. Any thoughts on whether I will be regretting that decision in a few months? Anybody know exactly what I have here? (Side note, loving the TBS live rock, all the cool stuff that has come in with them has been fun to watch and attempt to identify.

 

[Tatted Reefer]

It's hard to say 100% but when I had them they looked a little different. They were very thin and swayed with the current. If you touch it, does it suck back into the rock? If not, it may be some type of sponge. I ended up getting a lot of Digitate Hydroids before I gave in and treated my tank with Fenbendazole. It was a last resort but mine were getting pretty bad. If you only ever have a few, I wouldn't worry about them. Most people report that they just go away in time. I also had another tank with some and that was the case. Eventually, I just didn't see them anymore.

looked like these:

 

[Gtinnel]

Ive only had digitate hydroids in my tank and mine looked excatly like the pictures posted by @Dreamin' . Im no expert on hydroids and I'd assume there are probably a lot of different type but I'm not sure what you have are even hydroids, or at least not a type im familiar with.

The hydroids i had eventually went away on their own, im guessing something in my tank started eating them.

 

[Jamie9]

It's hard to say 100% but when I had them they looked a little different. They were very thin and swayed with the current. If you touch it, does it suck back into the rock? If not, it may be some type of sponge. I ended up getting a lot of Digitate Hydroids before I gave in and treated my tank with Fenbendazole. It was a last resort but mine were getting pretty bad. If you only ever have a few, I wouldn't worry about them. Most people report that they just go away in time. I also had another tank with some and that was the case. Eventually, I just didn't see them anymore.

looked like these:

Thank you, that's the first really clear picture I've seen, and mine is definitely a bit different. Mine sway in the current, but they are currently just sort of one tendril without the fuzzy bits off the side. One of them has recently branched into a fork at the tip. I'll put a glove on today and see if they retract back into the rock when touched. I do have several more traditional sponges that came in with my live rock, so you could be right about that. I sort of love that on just 5 pounds of rock there's all kinds of things that I can't easily identify.

 

[Jamie9]

No retraction when I touch them with a turkey baster.

 

[Gtinnel]

With digitate hydroids they will normally quickly retract back with any contact or even shining a light on them.

 

[Jamie9]

With digitate hydroids they will normally quickly retract back with any contact or even shining a light on them.

Thanks for that. I've definitely got something else then, which eases my mind as I've read about people's struggles with the digitate hydroids...but it was hard to find a good description of them. I'll look forward to keeping an eye on whatever this is in my tank to see what it does. I'm definitely going much heavier on live rock whenever my next tank comes around...it's too fun watching the things that pop up on them.

 

[Reginald Reefer III]

I have them bad in my ~1.5 year old tank. I'm almost certain these are the colonial type. They don't really seem to do much to the corals though.

EDIT - Mine look exactly like this that I just found on another website.

Manta Systems

Meet the R1 Feeder, browse expert reef aquarium guides in The Reef Library, shop our book store, or check out our podcast—everything from Manta Systems.

www.mantasystems.net

 

[Tatted Reefer]

Thanks for that. I've definitely got something else then, which eases my mind as I've read about people's struggles with the digitate hydroids...but it was hard to find a good description of them. I'll look forward to keeping an eye on whatever this is in my tank to see what it does. I'm definitely going much heavier on live rock whenever my next tank comes around...it's too fun watching the things that pop up on them.

Biodiversity is the best but sometimes comes with drawbacks. Glad it doesn't seem to be hydroids in this case! I'm willing to be some form of sponge which comes in so many different types it's hard to nail it down. Maybe as it grows out a bit, it will be more easily identified.

 

[twentyleagues]

Looks like a sponge to me and based off of what you are saying.