TROPICAL AQUARIUM FISHES 221 
depth of one foot or more. For tanks of moderate size—say 11 x 22 
feet—reinforcement should be by use of 14-inch steel rods, crossed on 
squares of 8 inches. The bottom needs two layers of these bars, one near 
the upper and one near the lower surface. This protects against both 
Fic. 161. CorrecT ARRANGEMENT OF REINFORCING STEEL, AND GALVANIZED IRON 
Form For WaTER Lity Pot 
Fic. 162. Woopven Form REApy FOR CONCRETE POURING 
The dotted blocks represent bricks or stones to hold inside form to same height 
as the outside. Note slope of inside form. 
