232 TROPICAL FISHES AND AQUARI A 



life-giving qualities and also produces uneven temperature for the fish to 

 pass through. Such an objectionable arrangement is shown in Fig. 209. 

 Aquarium water is directly heated in the small outside reservoir and cir- 

 culated back again. With this device the water intake may easily become 

 clogged, which soon causes the water to boil. This heating method is 

 used, but it is bad in theory and in practice. A better arrangement is 

 shown in Figs. 210 and 212, which is a complete hot water system not using 

 the aquarium water. The tubing is of copper, j4-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 ar- 

 ranged to occur in the rising side of pipe in the water. In Fig. 210 the 

 arrangement can be hooked over the edge of any aquarium and has the ad- 

 vantage that the aquarium does not have to be elevated to heat from 

 underneath. The first filling of the system is not always easy. Water is 

 poured in the funnel until it will take no more. Then the hand is placed 

 over the funnel and the pipe turned upside down. Turn upright again 

 and put in more water. Hold at different angles. When it will take no 

 more water, try heat under the coil. If the water in funnel moves up and 

 down, there is still air in the tube. Sometimes it can be removed by ac- 

 tively filling and discharging a fountain pen filler in the opening. When 

 the water remains still in funnel when heated, it is all right to use. The 

 funnel must always contain water, or boiling will soon occur. If a filled 

 bottle with small neck is inverted, stood in funnel and secured in some 

 manner, it will last a long time without refilling. The copper tubing 

 should be nickeled after bending, as copper is fatal in the aquarium. 



Fig. 211 shows a modification of the same idea with the pipe carried 

 through aquarium base. The little hollow hook at top of the hot water 

 system was devised by the writer to avoid the necessity of filling the 

 funnel, and to have the heater more concealed. The tubes within the 

 water are of glass, connected, by rubber, the end hook also being a 

 separate piece. By removing hook the system is easily filled. When heat 

 is on, vapor collects in top of curve, and when enough has collected to 

 force a bubble out, a drop of water is automatically sucked back to take 

 its place. The air space in hook also prevents any circulation between 

 hot water system and aquarium water proper. This system also gives 

 a higher percentage of heating efficiency than the outside form. 



