# Hydra in the aquarium

**URL:** <https://boards.straightdope.com/t/hydra-in-the-aquarium/614887>\
**Category:** Factual Questions\
**Created:** [March 6, 2012, 3:09am UTC](https://boards.straightdope.com/t/hydra-in-the-aquarium/614887 "2012-03-06T03:09:42Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\
**Post date:** [March 6, 2012, 3:09am UTC](https://boards.straightdope.com/t/hydra-in-the-aquarium/614887/1 "2012-03-06T03:09:42Z")

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Why does overfeeding brine shrimp cause a hydra infestation?

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**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\
**Post date:** [March 6, 2012, 3:22am UTC](https://boards.straightdope.com/t/hydra-in-the-aquarium/614887/2 "2012-03-06T03:22:13Z")

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Any chance they may have been introduced by live plants? Overfeeding can certainly make things worse…

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**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\
**Post date:** [March 6, 2012, 3:23am UTC](https://boards.straightdope.com/t/hydra-in-the-aquarium/614887/3 "2012-03-06T03:23:06Z")

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From a little nosing around, I get the impression that it’s not _overfeeding your pet brine shrimp_ that causes the problem, but overfeeding your _other_ pets (fish) _with_ brine shrimp. The hydras eat excess brine shrimp.

I think hydras are present in a lot of water sources and are often present in small numbers in fish tanks. They eat small invertebrates such as brine shrimp, copepods and daphnia (“water fleas.”) I presume that dumping a lot of brine shrimp into your tank can lead to a population boom of fat and happy hydras.

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**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\
**Post date:** [March 6, 2012, 3:27am UTC](https://boards.straightdope.com/t/hydra-in-the-aquarium/614887/4 "2012-03-06T03:27:46Z")

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> [@Sailboat](#):
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> but overfeeding your _other_ pets (fish) _with_ brine shrimp.

Yes, that is what I have been doing.

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**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\
**Post date:** [March 6, 2012, 3:31am UTC](https://boards.straightdope.com/t/hydra-in-the-aquarium/614887/5 "2012-03-06T03:31:17Z")

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> [@dolphinboy](#):
>
> Any chance they may have been introduced by live plants? Overfeeding can certainly make things worse…

I thought they came in from some vallisneria from [Tricker,](http://www.tricker.com/) but they are only in the tanks to which I feed BS.