Attack of the Hydra!

September 6th, 2008

Today, I had the misfortune to discover a new creature in one of my fry tanks. Quite a few Hydra are present in this tank, presumably introduced by feeding incredibly small fry foods, such as newly hatched brine shrimp. It’s also possible that they’ve been present all along, but couldn’t survive until I provided high-quality micron-sized protein powder for them (and the fry) to feed on.


Hydra are bad to have because just like their marine cousins (jellyfish, corals, and sea anemones), they feed off of small organisms, capturing them using their stingers. If they just stuck to water fleas or infusoria, I wouldn’t mind, but they will also attack newly hatched fry. That’s unacceptable. Now, I have shrimp in this tank, which some folks report will keep them under control, but nevertheless the Hydras are still present. Supposedly, they can be killed by using Fluke tabs, raising the temperature significantly, or by breaking down the whole tank, and sterilizing it.


I’m not going to break down the whole tank because feeding fry will just continue to promote their presence in the future. For the next couple of hours, I’m just going to watch them, since they really are neat looking creatures. But, then, I’ll start my assault on their lives. Suggestions welcome!

11 Responses to “Attack of the Hydra!”

  1. bdement Says:

    I had this same issue in my shrimp tank a couple weeks ago until I found this article:

    Over a few days I doubled, maybe even tripled his recommended dosage before doing a big water change. I noticed absolutely no ill effects on my shrimp or plants, and I haven’t seen a single hydra or planaria since.

  2. guitarfish Says:

    Great article, thanks bdement! Figures that I just netted all of the shrimp from the tank, and treated with H202 and Aquari-sol. So far, so good. (They shriveled up before my eyes)

  3. Kim Says:

    They look like a “Tingler Therapeutic Head Scalp Massager” I gave my daughter for a present one year:) What fantastic pictures and facinating creatures!

  4. PadreJP Says:

    Two possibilities. I have seen reports that Spixi snails (Asolene spixi) love eating hydra. I don’t know much about spixis but I’ve never heard of a snail that is a threat to a shrimp tank so I would imagine that would be the most natural solution.

    The other option is to follow the directions of the excellent article bdement linked in his comment above.

  5. Chris Says:

    I have heard of sparkling gouramis eating them, but I dont know if you would want to try that for fear of them eating your fry

  6. guitarfish Says:

    Thanks for all of the advise! My original treatment of Aquari-sol and H202 seems to have done the trick. I’ll move the shrimp back later this week, and the fry seem unaffected.

  7. Hydra spp. - Shrimp & other Invertebrates - Aquatic Plant Central Says:

    […] Re: Hydra spp. I just got rid of a batch of Hydras myself after getting them in a fry tank that I was feeding heavily to encourage growth. Apparently, it’s fairly common for that to happen. I got rid of mine using Aquari-sol and H2O2, although, I’d just try H202 by itself first. Here’s a picture of ones in my tank: Here’s my experience:…k-of-the-hydra […]

  8. Leona Says:

    I released a Clownfish into the tank filled with Hydra (and CRS + Yellow Shrimps). The 10G tank was literally swarming with Hydra, but in a week, they seemed to disappear. The only problem was that Clownfish also loved to feed on baby CRS and YS’s as much as it did on Hydra.

  9. guitarfish Says:

    Thanks for the info, Leona. Just to clarify, do you mean a clown loach? If so, I could definitely see them taking out the Hydras, as well as, the shrimp.

  10. Allison Says:

    I had hydras once. Adding gouramis took care of them. Pretty much any gourami (dwarf or the larger ones) likes hydra. I have ghost shrimp with two flame gouramis, and they don’t bother the shrimp.

  11. free mobile porn Says:

    looking for high quality adult social bookmarks?