50 



C. M. BREDER, JR. 



MATERIALS 



It is strongly recommended for all the 

 purposes for which these devices were 

 developed that only hard rubber or some 

 biologically inert plastic be used. In 

 fresh water, iron plumbing is adequate 

 for many purposes, but for sea water no 

 metals whatever should be used if any 

 degree of satisfaction is to be obtained. 

 Hard-rubber and acrylic-resin or vinyl 

 chloride-acetate copolymer plastics have 

 been used throughout for those parts which 

 come in contact with the water, including 

 the pumps. Also it is important to see 

 that no brass or other such metals are used 

 in positions over the aquariums in order 

 to prevent possible corrosion falling into 

 the water. 



In all cases involving the use of pumps 

 for aquarium purposes it is best to have a 

 spare standby duplicate pump and motor 

 unit as a precaution against the failure of 

 either motor or pump. It is then possible 

 to change such a unit in a few minutes, in 

 the case of accident, with no serious inter- 

 ruption to the operation of the system. It 

 is most convenient to use flexible connec- 

 tors between the pump and the rigid 

 plumbing leading to the aquariums. It 

 is then necessary only to unfasten two 

 screw clamps and insert the new unit in 

 place. This type of arrangement is shown 

 in figure 7. 



An additional advantage of this kind of 

 connection is that it dampens any vibra- 

 tions from the pump or motor, which tend 

 to travel throughout the system along 

 rigid connectors. The pump in figure 7 

 was suspended by four light cords, a means 

 which is also very effective in quieting such 

 small machines. 



TREATMENT OF WATER 



The treatment of fresh water for aquar- 

 ium purposes is too well known to warrant 

 comment in present connections and is 

 usually necessary only under special situa- 



tions. The maintenance of sea water in a 

 satisfactory condition is quite another mat- 

 ter. It is not the purpose here to discuss 

 the theoretical aspects of the chemical and 

 physical conditions of sea water. Such 

 matters may be found extensively treated 

 by Sverdrup, Johnson, and Fleming 

 (1942) and Harvey (1955). The follow- 

 ing is intended purely as a guide for the 

 practical application of principles which 

 have been found adequate to maintain a 

 variety of marine fishes. Under this treat- 

 ment regular reproductive behavior was 

 quickly established in both Histrio and 

 Bathygohius^ which had been reared from 

 juveniles. It also permitted a yariety of 

 volunteer algae and microorganisms to 

 establish themselves. Incidentally these 

 aquariums were kept under conditions of 

 no daylight, the illumination being sup- 

 plied by fluorescent tubes of the "warm 

 white" type necessary for satisfactory 

 plant growth. The periods of light and 

 darkness were controlled by a time swntch. 



The equipment found necessary for the 

 control of sea water consisted of a small 

 hydrometer, a colorimetric pH device, and 

 some simple titrating equipment. 



The filters were provided with bone 

 charcoal, and the bottoms of the aquari- 

 ums and reservoirs were floored with so- 

 called coral sand, and aerating stones 

 were placed in various convenient places, 

 but not in the aquariums containing fishes. 



The specific gravity and pH were taken 

 every day until the rate of change was 

 established and from then on were taken 

 at less frequent intervals. This rate of 

 change will vary with the quantity of 

 water, the bulk of the organisms con- 

 tained, and the temperature of the water. 

 At less frequent intervals titrations were 

 made to determine the variously called 

 excess base, titration alkalinity, or alka- 

 line reserve. This method, which meas- 

 ures the bound CO2, is not especially 

 accurate but is sufficient for the present 



