TROPICAL AQUARIUM FISHES 105 
If one is not blessed with a heated greenhouse or a room of warm, 
even temperature, artificial heating becomes necessary. There are several 
devices which accomplish this purpose, but only a few are satisfactory. 
In general those are to be avoided which concentrate the heat on a small 
portion of the aquarium water. This action drives out oxygen and other 
life-giving qualities and also produces uneven temperature for the fish to 
Fic. 74. InprrEcT EXTERNAL HEATER 
Fic. 73. Direct ExTERNAL HEATER 
Fic. 75. Inprrect SystEM THRouGH Base, SHowinc ImproveD Vapor EXPANSION 
Hoox Unper WatTER 
pass through. Such an arrangement is shown in Fig. 73. Aquarium 
water is directly heated in the small outside reservoir and circulated 
back again. With this device the water intake may easily become clogged, 
which soon causes the water to boil. This heating method is frequently 
used, but it is bad in theory and in practise. A better arrangement is 
shown in Fig. 74, which is a complete hot water system not using the 
aquarium water. The tubing is of copper, 14 inch inside diameter, and of 
thin walls. Before bending any such work to shape it should be packed 
quite hard with dry sand and the ends corked up. This prevents 
buckling at the sharp curves. At the very top of the loop rising from the 
heating coil should be bored a %4-inch hole and a small funnel soldered 
around this. All hot water systems create some vapor. If this were 
allowed to collect in the pipe there could be no circulation and boiling 
‘would soon take place. The two open ends need not be soldered together. 
They can be satisfactorily joined by rubber tubing. but this should be 
arranged to occur in the rising side of pipe in the water. This whole 
arrangement can be hooked over the edge of any aquarium and has the 
