anyone can help identify this aquatic microganisms?
It's a Rotifer, commonly called wheel animal It uses the hooks to attach itself to the fish's gills.
https://www.google.com/search?tbm=isch&amp;sa=1&amp;ei=1t4qXJS_Jaiu0gLYppCYBw&amp;q=rotifer+under+microscope&amp;oq=rotifer+&amp;gs_l=img.1.1.0l10.83680.92883..95716...0.0..0.181.993.1j7......0....1..gws-wiz-img.......0i67j0i10i67.8Yg5stvFiH4  

https://l450v.alamy.com/450v/k42bdt/rotifer-lapadella-apsida-female-free-swimming-microscope-freshwater-k42bdt.jpg 
I hope this helps