Are these jellyfish good or bad?

[yOyOYoo]

I am getting more and more of these every day! They are sometimes seen on the glass. And when I turn off my powerheads I can see many of them just bobblin and squirting around towards the surface of the water.

 

When I do water changes, should I siphon these guys out? Or are they harmless?

 

They look really cool, these mini jellyfish.

[Acoustic]

The animals are between one and two millimeters in diameter. These are organisms which are turning out to be relatively common. They are crawling hydroid jellyfishes, which do not swim, but rather move around the tank sort of like a small, soft, slow spider. They move by fastening on to the substrate with their adhesive patches. The tentacles are tipped with concentrations of nematocysts. There is a red eyespot at the base of each tentacle. These organisms become quite abundant in some reef systems, and then rapidly disappear without a trace.

 

A Japanese researcher, Dr. Yayoi Hirano, provided the following information:

 

"They are crawling hydromedusae, in the species Staurocladia oahuensis. There are about 15 species of this genus known in the world. All of them have branched tentacles, and can adhere to substrata, such as algae, by the tentacles, with the surface with eyespots facing upward. The tip of the lower branches are used for adhesion, and the upper branches have a few or more (depending on species) nematocyst clusters. Arrangement of the nematocyst clusters is a key to identify species. They reproduce asexually either by budding or fission, so under favorable conditions they often can become abundant in aquariums. This species has been found in a fish farm and also in a abalone aquaculture center in Japan. It seems the species has a high rate of asexual reproduction under favorable conditions. Even one jellyfish accidentally introduced in an aquarium may increase in a population of hundreds within a few months if the conditions are really good. It is also very possible that the polyp stage of the species lives on corals or rocks which may be brought into the aquaria. The polyps may form a dense colony if it is provided with much food. Within a short time the number of polyps may be very large, and the polyps may produce many jellyfish. The jellyfish and polyps will eat Artemia nauplii and copepods.

[yOyOYoo]

thanks Acoustic! I actually read that link myself, but I don't think thats what I have. *My* jellyfish definately swim. They squirt and move just like regular jellyfish. As for being on the glass, i'm pretty sure they only stick to it when they rest and they do not crawl like a spider...oh yeah and they don't have that red eyespot.

[surfy]

I have some swimming jellyfish like the one you are describing. They are harmless and usually don't last very long in our aquariums.

I would just leave them even though they will probably die.

[~_~]

Originally posted by surfy

I have some swimming jellyfish like the one you are describing. They are harmless and usually don't last very long in our aquariums.

I would just leave them even though they will probably die.

 

Yup, I used to have them, now there all dead

[Xanareef]

I have them as well, and the population has dropped drastically in the last month.

[Tataynic45]

I've had these and they dissappeared as well soon after. Looking at this thread, I had flashbacks of "Finding Nemo." lol