A movable catwalk above the pool permits 

 biologists to observe the behavior of fish in 

 the pool and engineers to install or service ap- 

 paratus mounted above the pool (Figure 3). 

 The center of the acoustic tile ceiling was mod- 

 ified to provide head room above the catwalk. 



The west wall is occupied by a rectangular 

 experimental tank and equipment table (Fig- 

 ure 4). The tank is 4 ft wide, 4 ft deep, and 

 15 ft long. This tank was constructed of 1-inch 

 plywood reinforced with polyester-resin bonded 

 fiber glass and supported by external bracing. 



The north section of the laboratory is oc- 

 cupied by two water tables used for aquariums 

 and small experimental tanks (Figure 5). A 

 700-gal portable fiber glass tank is often placed 

 in this area for holding live specimens. 



The south wall of the laboratory is occupied 

 by the recirculation system (Figure 6). Basic 

 components of the recirculation system, the 

 combination pool-reservoir (previously de- 

 scribed), sump, filter boxes, pump and delivery 

 systems, and various auxiliary components are 

 illustrated schematically in Figure 7. The 

 sump, constructed of poured concrete, is 2 by 



3 ft and 41/2 ft deep. Twin elevated filter boxes 

 (one inside and the other outside the labora- 

 tory) were constructed of 1-inch thick plywood 

 and are 3 ft wide, 2 ft deep, and 5 ft long. 



A continuous duty 2-hp self-priming pump 

 of 30 lb. working pressure is the heart of the 

 recirculation system. This pump functions 

 during the water cleaning with the diatoma- 

 ceous-earth filter and the recirculating of water 

 in the filled system. A standby pump is avail- 

 able for emergency. 



Most parts in the recirculation system are 

 either made of or coated with plastic to min- 

 imize maintenance and toxic materials. 



The 2-inch piping and valves used through- 

 out the recirculation system are polyvinyl chlor- 

 ide. Leaching of toxic materials into the re- 

 circulated water was inhibited by coating the 

 pool, sump, and twin filter boxes with polyester 

 resin. Pigmented polyester resin provided 

 background colors used in the experimental 

 pool (commercial pool paints should be avoided 

 because most of them leach chemicals that are 

 toxic to aquatic animals). The steel diatoma- 

 ceous-earth filter is sealed inside by a heavy 



Figure 3. — Movable catwalk above the experimental pool. The ceiling above 



the catwalk has been modified to provide head room. An elevated filter box 



i.s located at the far end of the catwalk. 



