106 GOLDFISH VARIETIES AND 
advantage that the aquarium does not have to be raised 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 actively fill- 
ing and discharging a fountain pen filler in the opening. When it works 
smoothly and the heat travels past the funnel, 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 heavily nickled after bending into shape, as copper is fatal in 
the aquarium. 
Fig. 75 shows a modification of the same idea with the pipe carried 
through aquarium base. The little 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 this the system is easily filled. When it is on, the vapor collects 
in top of hook, 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 hook-on form. 
pes 
JL a 
Fics. 76 anp 77. Direct Heatinc THroucH Pan anp THroucH MeEtaL Disc 
For the highest efficiency and greatest all-round satisfaction, note 
should be taken of Fig. No. 76. This is a 4-inch agate pan set in the 
cement base described on page 216. When making the aquarium it is no 
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. 77 shows a simple and fairly effective ex- 
