Growing in my filter medium?

[GlennJ]

While doing the partial water change and filter sponge cleaning found things growing in the filter sponge, small larva that appear segmented with some bristles at the segmented joints. Also found some others that appear to be pupa, shorter segmented tail section with bristles leading to a hard shell "head" that is semi-ovular with two "horns" protruding from the front(less than 1mm in length,the horns.) And two spots on the top of head that look like they could evolve into eyes .Dark brown to black in color, have not noticed anything weird flying or crawling around the house that could be the parents, nor them evolving any further than the pupa stage. Biggest larva or pupa are only 8mm long, so they exceed my cameras ability to attach a picture that would help. Any ideas what they are?

 

[SpaceFish42]

There's sure some weird things we find in filters. Once I found a baby cherry shrimp happily swimming around in my filter. Is it a freshwater or saltwater aquarium?

 

[GlennJ]

Freshwater with no new fish or plants added for at least 10 months, plus it's winter here since November so I don't think it was anything that came through the window.This tank has been going for 2 years in this home and never had these guys in the filters. Also had many tanks in my earlier life in this area and never saw these critters before.On the high note the Serps and the Cory's are enjoying them once I pluck them out and drop them in the tank.

 

[SpaceFish42]

It sounds like an aquatic thing, not an outside thing.