# Some kind of underwater catterpillar?



## Ckoizi (Jan 24, 2021)

Hi all! I’m hoping someone can help me 

we recently purchased a used aquarium tank from a private individual. Once we filled the tank and started the filter system, we noticed these strange caterpillar-like creatures at the bottom of the tank. They all seem to be dead.
Does anyone know what they are? And whether they’re a threat if we fill the tank with sand, coral and fish?

they range in size from 0.2 inches to 1.5inches-ish. There’s approx 20 visible in our 6ftx2ftx3ft tank.

we’re making a tropical ecosystem.

thanks in advance!


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## zeeshan (Jan 25, 2021)

This Looks Beautiful By The Way ;-)

This caterpillar Like creatures seems like some algae or Fungi try to touch it what it looks then.
In water eco-bio what i know this cant be harmful for any under water life, these can be converted into fertilizers for fishes to get food from maybe through symbiosis.


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## Legend1977 (Jan 29, 2014)

Ckoizi said:


> Hi all! I’m hoping someone can help me
> 
> we recently purchased a used aquarium tank from a private individual. Once we filled the tank and started the filter system, we noticed these strange caterpillar-like creatures at the bottom of the tank. They all seem to be dead.
> Does anyone know what they are? And whether they’re a threat if we fill the tank with sand, coral and fish?
> ...


I would get as many of them out with a net as you can. They may negatively raise your chem levels as they decompose in the water. And well, they are kinda creepy.


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## Legend1977 (Jan 29, 2014)

zeeshan said:


> This Looks Beautiful By The Way ;-)
> 
> This caterpillar Like creatures seems like some algae or Fungi try to touch it what it looks then.
> In water eco-bio what i know this cant be harmful for any under water life, these can be converted into fertilizers for fishes to get food from maybe through symbiosis.


Umm.. Algae? Fungi? Nonono.. that is like saying tree moss is like a grasshopper or some other bug. Algae does no not have bodies, heads, or feet. They are more like microscopic plants.


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## Mee (Jan 31, 2021)

There called bristleworms they eat the gish poop and stuff but if you overfeed they will begin to overpopulate the tank. Most people dont like them cause they look creepy.


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## Reefing Madness (Aug 12, 2011)

Mee is correct, they are just Bristleworms, you can remove them or not, they are not damaging to the system until they get really big.


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## Suesbi (Feb 1, 2021)

These Bristle worms 🐛 are usedp in Marine tanks you can get your answer about them by Googling Bristle Worm


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## RobertHuffman60 (Dec 13, 2020)

Ckoizi said:


> Hi all! I’m hoping someone can help me
> 
> we recently purchased a used aquarium tank from a private individual. Once we filled the tank and started the filter system, we noticed these strange caterpillar-like creatures at the bottom of the tank. They all seem to be dead.
> Does anyone know what they are? And whether they’re a threat if we fill the tank with sand, coral and fish?
> ...


A few species of caterpillars do indeed spend a good deal of time under water. It’s just that, as with many aspects of animal behavior, many caterpillars do not have these underwater habits and appear to spend all their time out of water


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## Arthur7 (Feb 22, 2013)

Can it be rat tail larvae? Or hover fly larvae





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