Bristle Worm Size

[mjleffler]

Hi everyone!

 

I’ve read a lot of conflicting information on bristle worms lately, mainly that they’re great at cleaning up the tank, but if they get too big, can start eating snails or even fish. Wondering if anyone has had any issues with big bristle worms bothering their livestock or if there is a certain size where they can become an issue. I would prefer if to leave it in the tank because I think they look cool, but would want to remove it it’s going to be aggressive. Here’s a few pictures of one I’ve noticed being pretty active in my tank. Don’t think he’s big enough to be a concern at this point but I could be wrong!

[WV Reefer]

5 minutes ago, mjleffler said:

Hi everyone!

 

I’ve read a lot of conflicting information on bristle worms lately, mainly that they’re great at cleaning up the tank, but if they get too big, can start eating snails or even fish. Wondering if anyone has had any issues with big bristle worms bothering their livestock or if there is a certain size where they can become an issue. I would prefer if to leave it in the tank because I think they look cool, but would want to remove it it’s going to be aggressive. Here’s a few pictures of one I’ve noticed being pretty active in my tank. Don’t think he’s big enough to be a concern at this point but I could be wrong!

Bristle worms are good guys....... Even the big ones. 😊

[Tired]

Bristleworms don't eat fish unless the fish are dying or dead. People who think they're predators have either seen them eating dead things and blamed them for that, or possibly have had some sort of aggressive fireworm go after their snails. Or mixed them up with the meaner eunicids. 

 

The worm you've photographed is the most common kind of bristleworm in the hobby. If fed heavily, they can reach 5-6" when stretched out, but they usually don't get that large. Expect more like 2-3" most of the time. If you overfeed, you'll get an unsightly overpopulation of them, but they're harmless otherwise. Just wear gloves when handling your rock (like you should anyway- sharp points and bacteria), because they do have bristles that will poke you. The worst they'll do to your livestock is annoy corals a bit by trying to take their food, if they live underneath the coral. Some fish will even eat small ones- I had a watchman goby in my old tank who would go after them. Sometimes they'd ball up too fast and he'd have to spit them out because he couldn't swallow them, though. 

 

As a general rule, most of the stuff that comes in on your rock is harmless-to-beneficial. Any given ecosystem has far more scavengers, herbivores, grazers, and other harmless creatures than it does parasites and predators. Your three big concerns are polyclad flatworms, mantis shrimp, and some of the parasitic isopods- all are rare, but do happen now and then, and can cause you some problems if you do get them.

[mcarroll]

16 hours ago, mjleffler said:

I’ve read a lot of conflicting information on bristle worms lately, mainly that they’re great at cleaning up the tank, but if they get too big, can start eating snails or even fish.

Something to worry about if you start seeing your snails or fish disappear....not when you read about it on the internet.  😉

 

Since you asked though:  

 

No.  Bristleworms can't eat your snails or fish.  Internet Myth #242,123. 

 

(You should feel free to mentally tag those sources you mentioned for the "quality" of info.)

 

16 hours ago, mjleffler said:

would prefer if to leave it in the tank because I think they look cool, but would want to remove it it’s going to be aggressive.

Bristleworms are related to earthworms and fill more or less the same ecological niche.

 

It's hard to imagine worrying about aggressive earthworms, isn't it?   😉 👍

 

(Google "giant earthworm" while you're at it....though it's not completely related to what we're talking about.)

 

16 hours ago, mjleffler said:

Don’t think he’s big enough to be a concern at this point but I could be wrong!

Correct!  Trust your gut!  😁

[mjleffler]

Thanks everyone for the responses, happy to hear they’re just beneficial!