THE AQUARIUM BUILDING 2/ 



expansion and contraction, for example by framing 

 the front of the tank with angle iron and permitting 

 the glass to bear against this frame. 



CONCRETE tanks: Concrete tanks can be con- 

 structed in a variety of sizes and shapes but in general 

 they are more satisfactory as large (200 gallons and 

 up) tanks. Even for this use they do not offer the 

 flexibility of metal tanks or the wooden tanks men- 

 tioned below. Concrete for tanks should be one part 

 Portland cement, two parts sand, and three parts 

 gravel (% inch). The cement should be tamped or 

 vibrated thoroughly to insure a tight, compact struc- 

 ture. After the concrete has cured, the inside of the 

 tanks may be painted with two coats of epoxy swim- 

 ming-pool paint. (This type of paint comes with the 

 paint and catalyst in separate containers.) 



If the concrete has been trowled to a slick finish, 

 prior to painting it should be etched with a solution of 

 one quart of muriactic acid to one gallon of water and 

 then washed and permitted to dry. Asphalt paint is 

 also used, but in the author's experience is not as satis- 

 factory as the above treatment and the black finish is 

 not always desirable. 



WOODEN TANKS: Highly serviceable tanks of a 

 variety of sizes and designs can be made of marine 

 plywood. This type of tank can be made with one side 

 of glass if a wooden or metal cleat is installed around 

 one side and a metal reinforcing rod across the top of 

 the open side. The tank, including the cleat, should 

 be coated on the inside with fiber glass, and the glass 

 side can then be installed with aquarium cement. The 



