20 



Marine Invertebrates 



ivm flrrH ""fn 1' 



water may be provided efficiently by hanging a loosely fitted glass tube 

 over the faucet and allowing a fine jet of water to strike the surface with 



considerable force (Fig. 23). Tiny air bub- 

 bles are carried down the entire length of the 

 glass tubing, the lower end of which almost 

 reaches the bottom, and escape through the 

 water, thereby aerating the fluid. 



A small but very efficient pump designed 

 by A. E. Hopkins (1934) may be con- 

 structed easily from a piece of celluloid. 

 The device consists of a small, motor- 

 driven, centrifugal pump enclosed within a 

 chamber from which it draws water (Fig. 

 24). The rotor (R) is cut from a piece of 

 celluloid y 8 inch thick and is mounted on the 

 shaft of y 4 inch glass tubing. The pump 

 receives water through the hole (X) in each 

 side and pumps it out through the tube (O) . 

 A larger tube (I) leads from the aquarium 

 into the pump chamber to permit continuous 

 replenishment of the water. The pump is 

 entirely water-lubricated and the only for- 

 eign materials used in its construction 

 are celluloid, rubber, and glass. 



Super saturation. Not all the forms commonly kept in marine aquaria 

 require aeration. As a matter of 

 fact many of them may be in- 

 jured or even killed by injudi- 

 cious aeration. Furthermore, 

 on account of considerable 

 pressure in the seawater pump, 

 water may be supersaturated 

 with air and become decidedly 

 toxic. To avoid injury to the 

 organisms such water must not 

 be delivered directly to the 

 tanks but should be allowed to 

 stand until equilibrium with 

 the atmospheric gases is estab- 

 lished. If the water must be 



used immediately it should be de-aerated by allowing it to fall on an 

 inclined glass, porcelain, or celluloid plate from which it runs into the 

 aquarium. 



Fig. 



means 



23. — Aeration by 

 of a jet of water. 



Fig. 24. — The pump for circulation and aera- 

 tion of water in small aquaria. After Hopkins. 

 I, tube leading from aquarium to pump cham- 

 ber; O, tube for excurrent water; R, rotor; X, 

 hole for incurrent water. 



