Help identifying a worm/grub/maggot like visitor to my tanks

[Ricky Flickenger]

I was looking in my tanks the other day and noticed a new visitor.

I was not able to capture any good pictures, so I can only describe in hopes someone can help.

At first I thought they were maggots. I was attempting to grow duckweed & azolla with minimal luck and the azolla had begun to die off. with the help of the millions of snails I have, my tanks are usually able to handle the added ammonia from rotting veg...plus no other fish in that particular tank right now...so I just left it as snail food. I suppose a fly could have come in and laid a bunch of maggots...but I have a clean apt and haven't seen any flies...it has also been very cold here in Seattle, so not many around.

What I noticed later were small, maybe 1/4 of an inch long, most a little shorter, slightly chubby tannish maggot like creatures. Lighter at the tail end, darker at the head, segmented like body like you might see on a caterpillar, and a dark brown/greyish like mantle of a head.

At first I freaked out and killed them (my system is all indoors, I don't want hoards of flies in my apt), then realized I should have tried to identify. Later I noticed more...but with odd behavior. I noticed something was moving down the glass, on the inside of the tank, holding on with only its mouth. It was moving at a snails pace and covered in some of the dead azolla, along with some living duckweed. Upon closer inspection it was the same kind of creature. At first I thought this was odd, then over the next several days after cleaning out all the dead azolla in hopes of getting rid of the creatures, I noticed a couple more hanging out in the tank. 

All of them had created some sort of shell out of the vegetation that was dead or floating in the tank. most were hanging out in these "shells" attached to other plants or surfaces by either their tails or mouth (I couldn't tell which) They were all IN the water, but not far below the surface, they don't seem to want to bury in the substrate. As far as I can tell, the only thing they are feeding on in dead vegetation/algae...no fish deaths yet.

I can say with certainty they are not mosquito larvae, or dragonfly larvae...they also wouldn't be likely to get in my house. I was thinking something that came shipped with the azolla...I got a bunch of other pond life with it...but it has been almost a month now, so I would think this would have happened sooner or I would have seen adult forms by now.

The only thing I can find online with similar behavior are caddisfly larva...but the creatures I found don't look like them...they are much more caterpillar/maggot like. They almost resemble blackfly larvae...but NONE of them are attached to rocks at the bottom feeding freely. They were all in their little "cocoons" hiding. 

If anyone has any ideas, I would appreciate them.

Ricky

[Ricky Flickenger]

So, upon further inspection with a friend and a lot of time online, it looks like they are aquatic moths. I never knew something like that existed! 

If anyone has more info on them, would love to here about it!

[Raychel A Watkins]

Sounds like Black Soldier Fly Larvae only they are not usually in the tank.  Google Black Soldier fly larvae and look at pictures and see what you think.  That is the best way to identify any type larvae.  Mosquito larvae aqre very thin and hang in the water they don't actually look like a worm that much.

[Ricky Flickenger]

Thanks Raychel, I thought it might be them at first as well. But am 100% sure it is an aquatic moth now. Once I was on that track I FINALLY found pictures that looks like what is in my tank plus the odd behavior of collecting floating detrus as an underwater cocoon. I also noticed the tell tale sign of arc shaped chewing on some mint leaves that were in the water...and some of those mint leaves are now cocoons in the water.