My aquarium (180 l) is inhabited by two Mikrogeophagus ramirezi, several Corydoras julii and some uninvited ranshorn snails.

Today three of these structures appeared. They are white, around 1 cm wide and between 1 and 3 cm long, very thin, and look foamy. They appeared rather quickly, I do not think they where there yesterday.

Can somebody identify what this is? Are these eggs, or something that I should be worried about?

I can exclude eggs from the ramshorn snails. I had those before, and they look completely different. But I never had fish eggs before, and I cannot find images of something looking like this.

Foamy white structure

Foamy white structure and a corydoras julii for size comparison

Foamy white structure and a corydoras julii and a Mikrogeophagus ramirezi for size comparison

  • Small update: The snails have eaten two of the three objects. I have now covered the last one with a small metal sieve.
    – Majiy
    Sep 7 at 10:09
  • en.m.wikipedia.org/wiki/Bubble_nest Have a look here. I do not know, if your fish are part of the mentioned kind of fish who make bubble nests :) and welcome to pets.SE :)) Sep 7 at 12:47
  • You have me stumped, I might suggest doing some night time investigating to see if there are other inhabitants in the tank you don't know about. That would be my recommendation. I can say with a high degree of confidence, this wasn't made by anything you listed as being in the tank. You also might consider taking a huge scoop of substrate during a water change and seeing what's in it. Could be leaches or some other similar but large invert. That would be my very rough guess.
    – Jestep
    Sep 8 at 20:35

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