The following images are from the sample that Damian collected 20/2/2018 on our walk to Branston Water Park viewed through the Zeiss IM microscope.
I had kept the sample fed with sugar dissolved in water over last 2 days and in sunlight and exposed to oxygen (opened top bottle).
All images with Bresser Mikrocam 5.0 5MP camera.
The black circles are bubbles.
Specimens killed with 10% formalin (20ml poured into 2 litre bottle) and then filtered with coffee filter to concentrate the specimen. Specimen mounted using water-based mountant.
I am particularly proud of the first photo. Darkfield achieved using Ph2 Phase annulus on Zeiss IM microscope with x10 objective and then I used GIMP to darken background a little (I used curves).
Andy
Darkfield image x10 objective Phase 2 annulus:
Same field as above, bright field, x10 objective:
Following images are all brightfield, x2.7 objective: 
