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Thank you Tony.
It is a difficult case. In addition to this site I showed photo to several Russian entomologist. There are two possibility so far:
1. Yours, Chironomidae.
2. Another one, Trichoptera.
Photo is from last year, 15-th of July, so in two weeks this eggs have to appear again in my pond. This time I'll try to do my best to rear it and find the answer.
Nikita