Some years ago, there was correspondence about putting fish in wells or cisterns that provided domestic water supplies, in order to keep the water sweet. The practice seems to have continued into the 20th century, at least, is on record in Roman times, and may relate to early references to salmon and trout in wells/springs.
There's a BBC page at the moment with pictures of Droitwich's long-wave transmitter building when it was first put up in the 1930s. The valves for the transmitter needed to be cooled by large amounts of water - 300,000 gallons of it. The tanks that held the water were provided with goldfish, the purpose of which was to stop algae growth. Plus ca change.
http://news.bbc.co.uk/local/herefordandworcester/hi/people_and_places/newsid_8366000/8366520.stm
Christine Buckley
