Found planaria(?) worm in tank- How worried should I be?

[AdoraBelle Dearheart]

I'm not 100% sure it's a planaria worm (hence the question mark) and I've tried without luck to get a photo of it, but I'm 90% sure that's what it is. Doing some reading now, but I trust you guys more than random blogs and articles. Do they pose a threat to my pygmy cory fry and other fish?

It's my 15.5g pygmy cory colony breeding tank, so stocked with dozens of pygmies and new fry appear often. Also housing eight otos and the last remaining elderly male guppy I have. I do encourage mulm and micro-critters in this tank, using almond leaves and letting moss and algae grow a bit wild since I think the otos and cory fry live on this stuff in between feedings. Plenty of other live plants too, but I do clean the substrate somewhat during weekly 60-70% W/Cs.

The fish all look fine, and I've only caught the one planaria so far because it happened to be near the top and stretched out from the tip of a leaf, and I scooped it into a jug. With everything else going on, I did the W/C pretty quickly and haven't had a good hunt for more, but I hear if there's one there's more.

I'm not panicking yet, but should I be thinking of worming the tank or something? No new recent additions to the tank either, I should mention, no new fish/plants/shrimp for a while.

 

[Back in the fold]

I’ve always found planaria in my aquariums. They usually have a little population explosion and then slowly dwindle away. I’ve never found them to be anything other than a curiosity but others may have a different planaria tale to tell. I would like to know where they come from to start with.

 

[AdoraBelle Dearheart]

I’ve always found planaria in my aquariums. They usually have a little population explosion and then slowly dwindle away. I’ve never found them to be anything other than a curiosity but others may have a different planaria tale to tell. I would like to know where they come from to start with.

From the little I've read so far, they come in with live plants, but since I haven't bought in any new plant matter for months, who knows? Perhaps eggs on plants or something? I don't even know whether they lay eggs, lol. The one I captured does have a bunch of little dots in the "belly" area, but whether those are eggs or internal organs, I dunno!

 

[Back in the fold]

That was my experience also. Nothing had been changed or recently introduced and by recently I mean several months. I have also had cyclops mysteriously appear. The only thing I can think of is eggs in commercial fish food. And Ostrocod seed shrimp too. Where do they come from ? Do they float around in the air ? Very weird how microorganisms get around.

 

[AdoraBelle Dearheart]

That was my experience also. Nothing had been changed or recently introduced and by recently I mean several months. I have also had cyclops mysteriously appear. The only thing I can think of is eggs in commercial fish food. And Ostrocod seed shrimp too. Where do they come from ? Do they float around in the air ? Very weird how microorganisms get around.

Or.... do they have eggs or something that come in with our tap water?

 

[GaryE]

I would suspect they have been there as long as you've had plants in the tank. I haven't seen any here, but if I let too much mulm accumulate or overfeed, they will appear. They're like disturbing opinions coming from the mouths of old relatives. Give them a context, and they are waiting.

I think they're hard on shrimp eggs. I believe I've seen people discuss that (I have no shrimp). But most eggs have defences against them, and they do no harm.

 

[Slaphppy7]

Planaria are expert hitch hikers; given their very small size, they can hide anywhere...even attached to fish that you bring home from the LFS

They generally aren't dangerous to fish, but pose a hazard to shrimp, snail eggs, and fish eggs

Here's a good write-up: https://fishlab.com/planaria/

What you found may or may not be planaria; but the triangular-shaped head is your first clue