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Hydra. This thing freaks me out, but I don't think it's bad?


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Is it NOT bad?  I found a larger one in my established and populated 20L (it was an amazing and graceful thing that I took out entirely, not breaking it up) and again today a small one on the glass.  I have fish and shrimp.  Lots of live plants and snails.  

The pests I don't mind are snails and detritus worms.  Pests that freak me out - everything else.  I don't hate hydras after reading https://www.aquariumcoop.com/blogs/aquarium/hydra , but I have a lifelong cringe because of reading Hans Christian Andersen's 
 "The Little Mermaid".  The polyps were monsters and I equate them with hydra!  I grew up with the book, not the video, and it affected me this much  lol

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Hydra is just… kinda… whatever… Really depends on your circumstances. 
 

I currently have it in my 55 Angelfish tank. That tank has Angels, Dwarf Rainbows, Cardinal Tetras, and Albino Cory’s. No harm no foul in that tank. 
 

If it was in my shrimp only tank, I wouldn’t freak out, but I would prefer it to not be there. Hydra feed on small things, so fry and shrimplets can become snacks. Hence why I would prefer to not have it in the tank I’m breeding shrimp in. 

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I sort of think of them like if an algae was an animal. They're either neutral or maybe even positive (they're free food for a lot of fish), but they can be unsightly and in theory can eat fry and shrimplets*. I remember @Guppysnail saying that they can go dormant when times are bad, like in the absence of food.

But my tanks that get the most baby brine shrimp have the most hydra. When I go a while without BBS, they die back. Are you feeding very small food? If so, you could cut back on it. Either way, I suspect that filtering out fine particles might thin their numbers by reducing their available food, but that's just speculation on my part.

* This is something I hear a lot, but usually with the caveat that 'but I've never seen it happen myself.' I'm not sure I've ever heard a firsthand account of hydra eating a fry or shrimplet. So who knows?

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On 6/22/2024 at 9:04 PM, Rube_Goldfish said:

This is something I hear a lot, but usually with the caveat that 'but I've never seen it happen myself.' I'm not sure I've ever heard a firsthand account of hydra eating a fry or shrimplet. So who knows?

Same. I’ve never personally seen it with my two eyes, but it’s talked about and I believe that it could happen. 
 

If you want to get rid of them, you can cut back on very small foods like @Rube_Goldfish said, you can use medication, or, I’ve also had luck with just the 3/8” hose from my siphon. Get the siphon going, and then scrape the glass with the hose and they come off and down the hose. You wanna be careful as if you break them both sides can regrow, and now you have two hydra when you used to have just one. But I’ve found that they don’t really escape the siphon and get carried out of the tank into a bucket. 

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I get this a lot when I overfeed BBS or small powdered foods. I stop feeding the tank and it goes away after a while. Never really caused me any issues other than needing to change the feeding strategy, which is just an annoyance. I wouldn't feed any food to the tank for a week, other than maybe Repashy Gel if you in a bind. The hydra can and will eat fish foods as they float by them, and maybe the gel wouldn't have that big of a problem since it keeps it's form.

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On 6/22/2024 at 11:04 PM, Rube_Goldfish said:

This is something I hear a lot, but usually with the caveat that 'but I've never seen it happen myself.' I'm not sure I've ever heard a firsthand account of hydra eating a fry or shrimplet. So who knows?

Community Breeding fish and constant feeding live brine shrimp I have hydra in all my tanks to one degree or another.  The only time I’ve seen hydra kill shrimplettes ir even teeny tiny new hatched CPD is when it carpets everything’s out of control to the point no matter where they go there is no safe landing spot or swim place that does not have dense plants carpeted in hydra. 
I’ve just accepted them as a natural part of an aquatic ecosystem and move on to things that actually need my attention. 

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Theres a few videos of them eating mosquito larva.   So for small fry, yeah it couuuld happen but would you even notice?  Like Guppysnail says, as long as your tank isnt choked with them.. 

Hail hydra!

 

Edited by daggaz
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I don't mind hydra. I had WCMM that had about 40 fry, only 6 survived. The other 34 fry got decimated by hydra. Survival of the fittest. Once there's not much for them to eat they start going out into cyst mode and kind of "disappear".

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