350 CARE AND FEEDING OF LABORATORY FISH 



FORMULAE FOR BALANCED FISH FOODS 



The prepared foods readily available are satisfactory in emergencies but they generally 

 lack some nutritional requisite, particularly vitamins. Two formulae are given below 

 which are currently used at the American Museum of Natural History. 



1. Aronson's formula : (See Zoologia 34:136, 1949) 



a. 2 finger bowl of chopped spinach. 

 2 finger bowl of chopped lettuce. 



Add a little water to the above and bring to a boil, then stop. 

 Separate the fluid from the solid by straining through a fish net. 



b. Take j lb. liver, chop fine, add spinach water and grind. 



c. Take finger bowl of dried shrimp, add Ij finger bowl of pablum. 



d. Add all the above mixtures together, with a pinch of salt. Mix thoroughly. 



e. Spread out thin on hard wood board, place in sunlight to dry. If too wet, add 

 more pablum to take up the moisture. 



f. When almost dry, put through fine meat grinder twice. For small fish, put 

 through grinder a third time. Will keep in refrigerator for a long time. 



2. Gordon's formula : (The Aquarium 1943, Vol. 12:87) 



a. Get 2 lb. beef liver, 10 tablespoons of Pablum (or Seravim), 1 teaspoon of 

 salt. 



b. Remove the connective tissue covering the liver, and the larger blood ves- 

 sels. Cut the liver into 2 inch pieces and chop until it is a liquid mash. If 

 available, use a Waring Blender (i. e. , liquidizer), which is rapid and thor- 

 ough. If the liquidizer is used, an equivalent weight of water must be added 

 to the liver, and the subsequent mash is strained through an ordinary sieve. 



c. Add the Pablum (or Seravim) to form a thick paste. Mix well. 



d. Place the mixture in small glass jars, and cover but do not screw the cover 

 on. Set the jar (containing liver-Pablum mash) in water, and bring the water 

 to a boil. Turn the fire off and let the jar stand in the boiling water about 

 one-half hour. This serves to coagulate the blood and other liver proteins 

 without destroying the valuable vitamins. It also pasteurizes it to some ex- 

 tent. Screw top on tightly. Keep in cool place (refrigerator) where it will 

 last a month, if not opened. 



The fishes are fed once each day, generally early in the morning, so that they have the 

 entire day to clean up all the food that is given to them. The uneaten food should be re- 

 moved at the end of the day, if possible. No further feeding should be made when there 

 is food left in the tank. The food may be added to the tank from the end of a scalpel, the 

 amount being about the size of one rice grain per fish (unless they are very large fish). 

 The fish will soon learn to come for the food, tear it apart, and eat it all. 



The approximate numbers of named species are: 

 Plants - 200, 000 

 Insects - 250, 000 

 Primitive vertebrates - 27 

 Fishes - 7, 400 

 Amphibia - 925 

 Reptiles - 3, 500 

 Birds - 10, 000 

 Mammals - 2, 700 



