TROPICAL AQUARIUM FISHES 



drying. For outdoor pools an inside slope of 2 inches is about right. 

 This would be. for a 7 x 9-foot pool, a top thickness of 4 inches, with 

 6 inches at the bottom. Base, 6 inches thick. For larger sizes add 1 inch 

 of thickness to walls and base. Indoor pools require no slope. In mak- 

 ing all calculations, allow ^ inch for thickness of finishing coat. The 

 forms should be levelled up and made absolutely true in the beginning. 

 It is a bad plan to depend upon the finishing coat to correct inaccuracies. 

 It seldom does it. Some considerable care is necessary to establish the 

 four comers at perfect level. Select one corner and measure each of 

 the other three from that. If the spirit-level is attached to a board, 

 its trueness should be tested by reversing the ends. In any case the 

 level should be reversed on each test. 



The concrete is mixed 1 part cement, 2 parts sand, 4 parts ^-inch 

 crushed stone or round stone. This is poured to within Yz inch of top 

 of form, beginning with the base and must be well tamped to avoid 

 bubbles and open spots. Those wishing to secure the best possible 

 results first place a thin skin of cement over the cinders so the water in 

 concrete will not seep into the cinder base, it being desiralble that all 

 concrete work dry slowly in order to crystallize perfectly. This prelim- 

 inary skin is as thin as possible and is applied the day before. It is com- 

 posed half each of sand and cement. If this is used, the lower layer 

 of re-inforcement may be laid directly upon it. 



ra ^ Q ft ." 6- ^ .' , * 4 ' ft" 



..4 



Fig. 164 



Fig. 165 



Fig. 160 



Fij. 164. Tile Set on Cement Mound. Fig. 165. Top Finishing Coat Broujht to Level of Form. Fie. 166. Guide-board 

 in Position for Inside Finishing Coat (VVhether or not tiles are used, this is the best method of linishing) 



Finishing coat should be applied within 24 hours, and is made 1 part 

 cement, 2 parts sand. Finish one side at a time, top edge first, inside 

 surface next, then outside, and the bottom after 4 sides are complete. 

 Begin by filling to top of form. Now take off inside form jrom one 

 side only. Lay a piece of perfectly straight board along top edge. This 

 makes an infallible gauge for thickness and straightness of finishing coat 

 (Figure 166). Here we might say that it is advisable to have an experi- 

 enced finisher do this work, but a resourceful amateur can do it. Now 

 do the outside in the same manner, the idea here being to have the top 

 bind with the sides while fresh. The outside being done last is less likely 

 to be kicked. Try to protect the job from rapid drying in the sun. 



