A MEDIUM-SIZED SEA-WATER SYSTEM 

 FOR THE LABORATORY 



By J. E. Mclnerney and W. S. Hoar 



Department of Zoolosy, University of Britisfi Columbia, Vancouver, B.C. 



Abstract. — A simple and eflBcient salt-water system which may be easily constructed 

 from readily available materials is described. Various ways of solving the problems of 

 contamination, aeration, removal of waste products, and temperature maintenance are 

 considered. 



The principal problems in maintaining 

 a closed salt-water system in the labora- 

 tory are as follows : 



1. Avoidance of contamination. 



2. Maintenance of adequate oxygen levels. 



3. Removal of waste products. 



4. Maintenance of temperatures. 



The sea- water system described here 

 provides a reasonably simple arrangement 

 of a size intermediate between the typical 

 home aquarium and the large public aquar- 

 ium. It has operated satisfactorily in our 

 laboratory for many years and has been 

 found useful in maintaining teaching and 

 limited research material. A schematic 

 representation is given in figure 1. Solu- 

 tions to the problems listed above are 

 achieved in the following ways. 



CONTAMINATION 



All parts are constructed of wood (filter 

 tanks and aquariums) or rubber or plastic 

 (pump, pipes, and connections). Where 

 it is necessary or more convenient to use 

 metal, these parts are coated with nontoxic 

 rubber- or oil-base paints. If it is im- 

 practical to paint exposed metal, then a 

 suitable type of noncorrosive stainless 

 steel is necessary. For example, the pump 

 shaft is frequently constructed of this 

 material. 



OXYGEN 



Adequate oxygen levels can be main- 

 tained in several ways. The most efficient 

 system involves a supply of compressed air 

 delivered through plastic tubing to air 

 stones with plastic rather than metal 

 stems. As an auxiliary source of aeration, 

 the water returning from the elevated filter 

 can be sprayed back into the aquariums. 

 Similarly the water supply to the filter 

 can be sprayed onto the filter bed by taking 

 advantage of the pressure supplied by the 

 pump. The amount of aeration required 

 is a matter of experimentation depending 

 mainly on the temperature of the water 

 and the number of animals. 



WASTE MATERIAL 



A useful and simple filter arrangement 

 is shown in figure 1. Water is removed 

 from a point as far as possible from the 

 clean-water inlet. It is pumped by a self- 

 priming plastic pump to the elevated filter 

 tank. An intermittent rather than con- 

 tinuous pumping action is achieved by 

 using a plastic float (in our case, a toilet- 

 tank float) in conjunction with a mercury 

 switch (similar to those found in furnace 

 thermostats). Details of this system are 

 shown in figure 2. 



The filter bed may be constructed of any 



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