Oh dang...Digitate Hydroids

[BonnieC]

So learning more about my tank, I noticed a couple weeks ago I have some spionid worms. I also saw some tentacles all over my LR and thought they were the same thing. Looking at them closer today, they are definately Digitate Hydroids. Up close they look totally different than the spionids.

And there are tons! What should I do?

 

[JustOneMore20]

I have some too....and I just use some tweezers to pick them off the rock. I know they can sting corals, but I haven't noticed any damage on my corals from these guys. I still try to pick them out when I see them though.

 

[thincat]

Just keep up with PWC and keep your water clean and that will keep them in check. They are filter feeders so it there isn't any food for them the will decrease in #'s.

 

[BonnieC]

Hmmm, but I have a big feather duster that gets fed Microvert. So I imagine it would feed them too. Ive done sooo many water changes bringing down everything in the tank. If anything, these things are multiplying...and fast!

 

[Zer0]

I would stop feeding your feather duster. There is no need to. Feather dusters get fed when you feed your fish. They will fan out anything in the water column that they can catch, most of the times little particles you can't see, and don't even know are there. Feather dusters survive just fine without supplemental feedings, and if anything, should be fed sometimes. Not every other day, or even more than once every two weeks. There really is no need to. A lot of those filter feeder foods cause nitrate problems and cause tank water quality to diminish. Seen it happen too many times.

 

[thincat]

If you really must feed your duster, spot feed it with just a squirt of food and no more...

 

[thincat]

Bonnie, I was up late last night and was doing some reading and came across this snail and thought about you and your situation. I hope this might help you with your Hydroid problem.
Keyhole Limpet snails – Diodora is the most common

Distribution: Most are from Baja California
Water condition: 72-78ºF, sg 1.025, pH 8.1-8.4
Active time: Nocturnal
Size: up to 3 in.
Diet: Herbivore
Zone: Most like rocks, but will sometimes congregate at the sand line on the glass and they will clean below the sand line.
Pros: They are great for eating hydroids and will also feed upon all forms of microalgae.
Cons: They have been known to sometimes graze on Acropora, Montipora and other similar species.
Additional information: There are dozens of different keyhole limpets in the hobby and close to 200 species in total. They come from all over the world but Diodora is probably the most common genus. Common keyhole limpets found in the hobby range from a few mm to 3 inches in size. The information bellow is for the most common species found in the aquarium trade. For more accruate information, consult Shell Catalogue and Sea Life Base. The image bellow is actually Megathura crenulata.
Photo: JP McKenna

 

[BonnieC]

Hmmm, interesting! Thanks

 

[BonnieC]

Where did you find that? Im trying to see who sells em.

 

[Kurt_Nelson]

It sounds like maybe you have Colonial Hydroids and not Digitate. Colonial Hydroids looks like clumps of little mini feather dusters (kinda), where Digitate Hydroids are a single string-like "arm" that extends out looking for food - usually at night. You normally can't see really where "string" is coming from and it is very sensitive to light and movement and retracts amazingly fast when it senses you are coming after it. Really cool things to watch, really.

Both of them are said to be "bad" hitchikers, but I've had/have both and think maybe the "danger factor" of them is a bit overstated. At least in my experience they are. The Colonial Hydroids will definitely spread if conditions are right, but nothing like aiptasia. I have a few clumps of Colonial Hydroids here and there, and new ones sprout up occassionaly. From time to time I go at them with my long handled tweezers like JustOneMore20 mentions. You can grab a clump of them and kind of twist and pull to get them at their base.

I don't doubt they pack a sting, but I've had some pretty defenseless soft corals (Sansibia/Anthelia) grow right up around them and they weren't bothered a bit. In fact, they overgrew the Hydroids which I was surprised at because they won't overgrow anything else in my tank!

The Digitate Hydroid I had was living within a colony of Pipe Organ Coral and didn't bother it a bit either. Eventually it just up and disappeared. Not sure if it died, or moved on somewhere else. But it was the only one I'd seen and I haven't seen any other.

Guess my point is that while they're worth watching and plucking from time to time to keep in check, unless your tank is completely overrun with the things, I wouldn't worry too much about them. A clump here and there won't hurt anything.

 

[BonnieC]

Hey Kurt! They are definately digitates then. They are single threads and react like you said. I have a lot of them but they aren't clumped together. They pop out of the holes on my LR and I have no idea what their base looks like.

The wierd thing is when they come out. They actually come out during the day sometimes. But not always. Since they are supposed to hide from light, im guessing they are hungry.

I'll try and get some video and a count of how many I see. It's hard to get anything clear because the tank is so bowed.

 

[Kurt_Nelson]

You might want to post up a picture if you can get a good shot. Seems like from what I've heard, Digitate Hydroids are not the most common thing to have in our tanks, and to have a LOT of them would seem kind of odd. There are also some type of worms that extend a long single "tentacle" in search of food. I have a few of those, but can't really describe it - other than the worm's tentacle is maybe a 1/16th inch in diameter while the Digitate Hydroid is literally the thickness of a very thin thread.

 

[cabezon]

are these the worms that let out a long string of mucus and then draw it back in? I saw one reeling in a pod once. I have a bunch in my tank.

 

[Kurt_Nelson]

Those are spionid worms. What I'm talking about is a worm that actually lives within the rock. Kind of like a spaghetti worm or a peanut worm.

 

[thincat]

I believe it's a vermitid snail:Vermitid Snails pictures from aquatic photos on webshots

 

[Kurt_Nelson]

Sorry... I meant to say "vermetid snail" but got thrown off by Bonnie's original comment about spionid worms.

Yeah... the ones make their own little tube that pokes you in the fingers when you're not careful, and cast out the mucous strand are vermetid snails. The spionid worms have a pair of feeding tentacles that comes out of the tube, or hole where the thing lives. it doesn't use a mucous net or strand.

 

[BonnieC]

Yeah, mine don't throw out a mucus net.

I do have some spinoid worms as well. They have little sand encrusted tubes and have 2 thin tentacles that come out.

I originally thought the hydroids were the same thing as the spinoid worms with the little tubes. Except they only had the one tentacle. They are so thin, maybe just a tad thicker than a stand of hair. So I didn't even notice at first that they were different, other than they come out of holes in the rocks. So I looked at them up close and they look exactly like this: http://www.mikesreef.com/images/critters/Hitchhiker17.jpg

Ill try and get video and pics. Funny thing is, they haven't come out in two days which is unusual. So either the new cleaner shrimp is eating them, or the just arent hungry and are only coming out at night now. Ill keep you updated.

 

[melosu58]

Xtalreef

 

[Kurt_Nelson]

That's a great photo you found there Bonnie - best one I've seen. And that is definitely a digitate hydroid! Guess you just got "lucky" with your rock! I was worried when I saw one in my tank, but then after "chasing" it a few nights I realized there wasn't a single thing I could do about it! And then as soon as I just accepted that it was there... it was gone!