Urgent Please help identify aggressive unknown colony in substrate

What kind of hydroids and could you find reference to them on the Internet for us? I've never seen hydroids as large as these. What size were the medusas? Typically they come from smaller hydroids and the medusa are on the smaller side.

To the OP, do they look like they are all attached to each other somehow? To be colonial, they have to be attached to each other. I thought they were looking like individuals.

 

I'm sorry for my lack of completeness. They are Hydrozoa not hydroids. They would be inter connected by a thin branch/membrain which would be easily broken if the substrait is disturbed.
I do not know the exact species. A friend of mine had them and a biologist friend of his from sea world ID'd them. The give away is the short stalks and few long tenticals most often 8 tenticals but could be only 4 or 6.
Most of these species can give a severe sting to a human as well.
My friend track his as coming from Figi LR.
He never saw swimmers but when he did a tear down he found some in the sump media.
He started from scratch afterwards got rid of everything, including tank, all equipment, live rock, and corals.
That is an extream action but that's the kind of guy he is.

 

To the OP, any chance I could get some from you if I pay for shipping?

Thanks lvlountainman.

 

Sorry for not chiming in long ago I didn't see there was more than one page of replies and thought I never got a response. Some answers to a few questions I recall. When attempting to scoop one out of substrate, it retracted in a split second completely under the substrate. I tried to dig deeper and a hole appeared where it was as I'm guessing it retracted all the way to the bottom. I didn't pursue any further due to not wanting to risk making the problem worse by messing with them. They are in groups behind the rocks where the light doesn't shine and most of them disappear when the lights come on. Also, there are a few individuals up higher in the lr itself, so that probably eliminates the colony idea. Also, when stretching for a snail, the body gets thinner and longer and will stretch pretty far. As far as how they attack a snail, the first one to go is the best example. First, I noticed a tentacle o two reaching towards and then touching the shell and maybe feeling around. A while later I came back and found the creature stretched towards the snail. A little later still I found the snail inside the center of the pod big end first and nearly halway inside. Was the type of snail with small long diamond shaped shells. Not sure what happens next... I turned the light on and the creature slowly spit the sail out, but never hid and remained in contact through its tentacles. This patter has continued, while feeding, they appear less concerned about the light. Also, during or after feeding, I don't know which, the tentacles turn a deep red color. They vary in size, the largest ones are probably close to an inch tal above the substrate, maybe a hair over a quarter inch thick. The tentacles may be over two inches on some and appear to flow with the current, but must be able to be controlled by the creatures. To get closer to a snail I think they are able to move over a period of time, but I can't actually confirm that. Th tentacles are clear but can be a purple color. Looking through them tiny white specs are visible and they have slightly enlarged rounded white tips. The body is also more or less transparent and looks to be very soft and delicate. The body is perfectly round with a slightly rounded top that opens in the center with tentacles around the outside. I've never counted the tentacles but would guess at least 8, but more like 12 plus. The body is tan to brown in color with a very very distinct diamond pattern on every one. As far as shipping them to anyone, right now I am not going to disturb them until I know exactly what they are. I am new to reef tanks, but most of my research tells me that a lot of problem creatures multiply, split, become swimmers, spawn, change behavior, etc. when disturbed or attacked. If we find out what they are and I find I can share without taking any big risks i'd be happy to. The peppermint shrimp appear to constantly hunt them, but as soon as anything touches them they retract. At first, I thought they were decreasing in numbers and size, but now theorize that there are just more of them hiding because of the shrimp and crabs constantly crawling around back there and disturbing them. These are incredibly beautiful and fascinating creatures so observation is the only thing I've done besides the one time I tried to scoop one up. If they stay in the dark and only hunt snails, then they are probably some great scavengers for the dark dirty places I can't reach. My concerns are serious too though. The tank has been running 8 years with previous owner came with zero cleanup crew and just a really large long branchy leather, a large toadstool, and a ton of actinodiscus mushrooms(probably a bigger problem), and at least a dozen skeletons of coral that didn't make it. So my biggest worry is that after eating all my snails, will they start hunting more valuable things like fish and corals. Any other feedback on the tank is also appreciated as mentioned this is all brand new to me and everything helps. My next questions will probably be advice on acclimating everything to the new light I ordered. The AI vega that just came out should be here by next Friday, I can't wait. The only sad part is the guy I talked to said I should start at 20% and only increase by 5% per week so I'm looking at about 4 months til full power. And btw will be watching closer for replies now that I see there's more than one page. After looking at all the forums,you guys seem to be on top. Thanks for all the replies and will read through them and do more research as soon as I can. For tonight a 25% water change and cleaning my canister and some new gac. Trying to get nuissance algae under control as well, but one think at a time. Thanks again everyone!

 

I found this link and they do indeed look like hydroids.

Hydroids and Jellyfish - Starfish Photos - Hydrozoen und Quallen

You are going to have to think about an intervention to rid the tank of them, or they will sting your corals, inverts and smaller fish.

 

Still not convinced. Haven't seen anything that even slightly resembles the top of these creatures. One that looked closest I found was listed as toadstool mushroom polyps or spawn or something but was a bad pic. The top doesn't have an open center like all the different hexacorals and octos or sea anemones or hydroids or jellyfish. Looked at every pic in that link. Lots of resemblance to individual parts, but nothing even close to the combined package. When first rising out of the sand they look like little space ships with smooth rounded tops, then top opens a little and the tips of a few tentacles appear. Over time they open all the way on top with long tentacles around the outside edge, and a very distinct raised round bump sticking up in the center, looking even more like something from another world. There is also one little orange dot on the side of the center just outside the bump in the center. I will try to post clearer pics and see if that helps with an id. Tried again to catch one last night and couldn't even come close. Tried tweezers first several different ways and can't decide if they are too fast or slippery to catch before they disappear under the sand. Then I tried the shovel attachment on a multitool and attempted to sneak under it from a distance. Right away it knew there was a threat, retracted halfway and I tried patiently waiting til it was off guard to move closer to scooping it up. It caught on quick and disappeared. I scooped any ways and nothing was there aside from a couple black round snail shells a little larger than a pea. Possibly the creature but highly doubtful in my mind. I buried a fish net in the substrate and will see over time if one moves into the area so I can pull the net out with one retracting right into the trap. This may take days or weeks if it works at all. My observation leads me to believe these creatures act intelligently. Like how quickly it decided me digging in the sand was trouble, but not right away. After three attempts at waiting for it to open then moving a hair closer. I was probably 3 inches away and only an inch deep in the sand. I am also starting to believe they can move sideways under the sand bed. When disturbed by a crab, one disappears and seconds later I notice one I didn't see before of similar size and color 3 to 6 inches away. So far I don't believe my corals are in danger because it appears these creatures choose to stay where its dark. And my firefish has recently decided that the back of the tank is a good hang out and drew the cherub angel with him. They don't appear at all concerned or affected by them, although I've never seen direct contact either. These are special creatures, I just don't know who to ask that would be able to positively identify them so that I can do some serious research. I've don't a lot of digging around and understand I may never find an exact match, but think I should be able to find something close enough to convince me. I will post some new pics right now if I'm able or add to the channel at dbarter8872 - YouTube . Thanks again for the ideas and I'll look forward to more. Also if I get a chance I'll do some more searching around for every suggestion I didn't see posted before. Also, will try to make a list of creatures with matching parts to help paint a better picture. I know I've seen similar tentacles and pods on other creatures maybe someone with a good imagination can use that to help.

 

I give up. I am a nice guy and offer my assistance when I can. I am not perfect and do not know nearly enough to call myself well experienced. However, You have been given EXCELLENT ID's and ADVISE. And you have done nothing but call everything false. I am done watching this thread.
Hopefully next time we can do better for you with a diffrent species or issue.

I find it funny that someone new in the hobby always believes they have found something never before discovered.