Water Critters Technique

[Olympusman]

One issue when photographing pond life is slowing the little buggers down for photography. Charlie and others have put together flash systems to freeze the action. If you are using tungsten illumination, you may have to slow down or euthanize the creatures chemically. I use use several options.
4% solution of Glutaraldehyde - Effecyive for microcrustaceans such as Daphnis and Copeods. It may take several minutes for them to expire. Does not work well on protozoa since it causes the specimens to contract and become deformed. Usually dose one drop Glutaraldehyde to one drop of pond water.
Epsom salts - You may have to play with the concentration.
Cupric Acetate - Fairly effective with protozoa. I use a 3% solution with one drop Cupric Acetate to one drop pond water. Minimal deformity.
Methyl Cellulose - Increases the viscosity of the sample to slow down the creatures.
I have also been expermenting with using a centrifuge to increase the density of the sample. About ten minutes of centrifuging concentrates the sample to a pellet at the bottom of the vials. Carefully pipette the clear solution out before pipetting the pellet.