TROPICAL FISHES AND AQUARIA 



233 



For the highest efficiency and greatest all-round satisfaction, refer to 

 Fig. 214. This is a 4-inch agate pan set in the cement base described on 

 page 107. When making the aquarium it is little extra labor to set this in. 

 For aquaria already constructed it is somewhat of an undertaking to cut 

 a sufficiently large hole, but it can be done and the pan cemented on top. 

 Fig. 213 shows a simple and fairly effective expedient. After hole is cut in 

 slate, pour in lead or tin. When the metal is poured, use a form made of 

 putty to make a circular dam so that the surface of metal will come as 

 high as the sand. The object in using the inverted pan is to have the 

 heating surface come just above the sand. Then the heat is the most 

 efficient as well as fairly diffused and does not interfere with the roots 

 of plants. The objections to this type are that the aquarium has to 

 be raised and that there is an occasional drip of condensed water caused 

 by combustion. The best flame to use is a small gas Bunsen burner. They 

 may be had of some scientific apparatus concerns or dealers in German 

 aquarium supplies. No more than the tip of flame should be allowed to 

 touch the heating surface. Even this is not necessary in system shown 

 in Fig. 214. Smells are caused by having the flame strike directly against 

 a cool surface, which interferes with complete combustion. 



Heat Control. In a room where there are wide changes of tempera- 

 ture, particularly when these dip to the cold side, it is desirable to have 

 some means of heat control. To start in the very 

 simplest way first, an aquarium may be kept noticeably 

 warmer over night by covering with a thick blanket, 

 quilt or any warm fabric. If near a window the curtain 

 should be pulled completely down. Another help for 

 any aquarium near a window is to have a sheet of glass 

 standing nearly vertical on the aquarium base and lean- 

 ing against the top. This sheds much of the cold 

 air which constantly falls from a window in cold 

 weather and rapidly chills the water. 



Tropical aquaria, if not too small, may be kept at 

 a satisfactory temperature while standing on a board on 

 the radiator of a hot-water system, the heating result 

 not being so extreme as might be expected. 



An occasionally used means of controlling tem- 

 perature is to heat by gas and use a thermostat to regu- 

 late gas flow. See Fig. 215. This is placed either in the 

 water or tightly against the outside of the aquarium, and 

 insulated from the influence of surrounding air by plenty of wool or cotton 

 batting. It contains a large body of mercury over which the gas passes 

 through a small space. As the water rises in temperature, the mercury 



Fig. 215 

 Gas Thermostat 



