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Yes that is a damselfly nymph. I had them. They are fascinating and grow into gorgeous damselflies. @Torrey  has them. If they are not native to your region as mine came in shipped plants I can’t raise and release. They were in my shrimp and bladder snail tank and took their tole. They are VORACIOUS predators and will eat anything they can catch including small fish and fry. Netting them out is the only safe removal. Anything that will kill these hardy nymphs will decimate all other inhabitants. They burrow into substrate so replacing substrate and quarantining all plants is effective for removal. They can live in your tank for up to 3 years. Life cycle at this stage depends on how much they get to eat. 

Welcome to the forum. Sorry it’s under stress over an uninvited guest. 

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I was thinking that it's a Mayfly larva, but what do I know? At any rate, it takes two to fly into the air above the water to mate and then fly onto the top of the water to lay eggs, and then they die. If that is the only one in your tank, it doesn't have a mate so it can't breed, it'll die on its own soon enough. If you have fish large enough to eat it, one of them will.

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My 10 gallon is stocked with embers, emeralds and growing guppies so everything would be considered small and vulnerable.


Scary to think they were in danger and where it even came from. That tank has been in place for over a year but I got some Java moss recently. That's been the only new addition in some time.

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On 12/8/2021 at 6:27 PM, ElTacoJr said:

Sorry for the lack of introductions but I just found something in my 10 gallon that I don't recognize. 

Does anyone know what this is?



See the 3 fans at the 'tail'?

Those work like lungs for damselfly larvae. Damselfly larvae will prey on the tiniest fish: small guppies, small endlers, newly molted shrimp. Therefore, if it is in a breeding setup, it will significantly reduce your fry that survive by culling the slowest, most vulnerable from your stock.

As adults, they are our friends. They eat a huge amount (for their size) of mosquitoes, whiteflies, thrips, and other threats to our plants (and our skin).

I ended up with ~a half dozen damselfly larvae in some plants I got from an outdoor pond supply place (I wanted the Mexican azolla and accompanying mosquito larvae for live food).

Despite the damselfly larvae, I still ended up with enough danio fry and endlers that made it to adulthood to sell over 300 fish to my lfs.

I started re-evaluating all of the panicked "HAVE YOU SEEN THIS IN YOUR AQUARIUM" after Cory convinced me 'pest snails' are beneficial. He has been correct, almost all the 'pests' have a place in healthy ecosystems. 

If I were to breed something rare, that needed to have all fry protected because they are endangered, I would ensure no damselfly larvae were in the tank.


My spouse who **hates** bugs has been proactive in helping maintain our indoor damselfly population because for the first time since my spouse moved to the High Desert, we had ZERO flies, fruit flies, thrips, or any of the other 'bugs' that annoy my spouse with our indoor garden.

Payment of a few fry and a slow couple of adult fish has been a minor price to pay for our 'bug free' home.20211212_200611.jpg.4d07e59c65efe16c33e9911160092d8b.jpg

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