Use dechlorinated bottled water. The greater the amount of water, the less it needs changing. No more than 50 leeches should go into a 2.5 litre container. It will be good to change water every two days.
The leeches will survive quite happily in a refrigerator or in a cool place, provided the temperature does not exceed 15°C. Special care and attention should be taken if the leeches are to be used in a heated hospital ward. Keep them as cool as possible until they are needed. Never put leeches into direct sunlight.
A lid is essential. Leeches are amphibious and like to crawl about. Perforations are advised but they must be very small indeed, as the leech body is elastic and capable of going through remarkably small openings. A cloth cover secured tightly with string, rubber band or tape is useful. Do not overcrowd.