Purification of Paramecia
(Source: B. Trevarrow from Zebrafish Book 5th Edition)
Contamination is a recurrent problem with paramecia cultures. Here is a simple technique that allows the isolation of paramecia or other motile micro-organisms from non-motile or more slowly moving organÂisms that may contaminate the culÂture.
1.    Prepare a number of small diamÂeter glass tubes (about 5 cm long and 2-3 mm inside diameter) that are filled with loosely comÂpacted glass floss. The floss should be inserted 3-5 mm in from each end (see below). To insert it, cut a strip about 2-3 mm wide and about 5 cm long and draw through the tube with a wire hook or tubing with a notch in it.
Device for purifying paramecia.
2.  Sterilize the tubes.
3.  Suspend a sterile floss-containing tube in a sterile 60 mm Petri plate with a piece of tape. The tape does not need to be sterile. Avoid touching the ends of the tube.
4.  Using a sterile pipette tip, add sterile 10% Hank's to one end of the tube. Leave space (about 2-3 mm) in the end of the tube for the addition of the impure paraÂmecia culture.
5.  Add a droplet of the imÂpure paraÂmecia culture to the same end of the tube filling the 2-3 mm space.
6.  Occlude the culture-conÂtaining end of the tube with a small piece of modÂeling clay (e.g. Plasticine).
7.  Wait a few hours and the paraÂmecia will appear at the open end of the tube where they are obÂservable with a disÂsecting microÂscope and can be isolated with a sterile pipette tip. Do not wait too long or other slower movÂing organisms may catch up.
8.  Add the isolated paramecia to a sterile culture and no other orÂganisms should be present.