Green Worms or worm-like algae???

[plutoniumcaterpillar]

I have a 20gal planted tank that has these strange green, worm-like things living mainly on the decorative caves in the tank, but also on the glass. They appear greener on the caves, but still have a greenish tinge to them when appearing on the glass. When looking at them on the glass their bodies appear segmented. I really thought they were a type of algae at first because they appear to be slightly fuzzy like algae when viewing them on the caves. But after viewing them for awhile you can see they extend their heads out past the algae-looking part, almost like a sword and sheath, and wiggle around a bit. I've also seen them floating around the tank writhing through the water.
They are very numerous and vary in length from 0.5 to 1cm, and 1mm wide.

Does anyone have any idea what these are and if they pose an issue to my tank? And if I should do anything about it? Thanks!

Tank species:
Java Fern
1 very old catfish, possibly an upside down cat (6" long)
3 corydoras

 

[Gillie]

They are some kind of aquatic larvae. I can't remember what kind but, they remind me of caddis fly larvae.

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[dcutl002]

I cannot tell from your picture, but I suspect that you may have Freshwater HYDRA. I had some at one time and they did not hurt anything, but they multiply. I had a pair of Blue Gouramis that ate all of them.

Update: I took a closer look at the pictures and i do not think you have hydra. whatever fish you add with your catfish should eat them for a nice tasty treat.

 

[plutoniumcaterpillar]

Thanks for the replies!

I did a 25% water change shortly after posting this thread, and the next day I noticed a significant drop in the numbers on the tank decorations. Not sure if this had anything to with the water change or if it was just coincidental, but they don't seem to be posing any issues. We'll get some non-bottom feeders soon and maybe that will take care of any population booms we get in the future

 

[dcutl002]

I have some planaria in my substrate, not sure how they got there, but my Gourami's name a meal of them from time to time. Free food.


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[plutoniumcaterpillar]

Meant to post this a while back, but the mystery has been solved! The day after my last post, I went back to feed my fish and I noticed all these little gnat-like flies stuck to the lid of the tank, as well as another decrease in the number of "green worms" in the tank. They must have been the larval stage of this fly species and all matured together, and committed mass suicide on my tank lid XD Glad that is figured out!