sure looks like a diatom; for example phaeodactylum tricornutum

any information about size? which medium are you using?

http://www.algaebase.org/search/species/detail/?species_id=39314

 Thanks! I used the camera Goryaeva. The area of the square in the figure of 0.0025 mm, so I think that the size of the microorganism 30 micrometers.

I used medium Tamiyya and I noticed that Chlorella vulgaris cells grew much worse than usual.

it sure looks like a pennate diatom sp. potentially Navicula sp.

Thanks for the help!