TROPICAL AQUARIUM FISHES 65 
large stock where it will be kept in good condition and will be available. 
If the spring has a good flow, the tempering pool can be kept comparatively 
free of ice and fish can be caught as wanted all Winter. 
With the use of ground-level ponds the snake, frog and rat have 
good chances of enjoying the luxury of feeding upon goldfishes, unless the 
vigilant breeder adopts effective means of keeping these pests under 
control. 
Ass stated in the former chapter, it is advisable to provide shade for 
the fishes. Trees at the right places would be beneficial but this cannot 
often be arranged. Aquatic plants, particularly water-lilies, are to be 
recommended. Plant life in a clay-bottom pool should be strictly limited 
to a few species, as some plants once obtaining a foothold can only be 
eradicated with the greatest difficulty. The plants to be used are Giant 
Anacharis, Myriophyllum, Cabomba, Ludwigia and Water Cress. All of 
these are desirable and furthermore find ready sale. Cyperus such as 
shown in illustration may be kept in pots. 
Specially Equipped Breeding Establishment. A more elaborate 
and considerably more expensive establishment is shown in our figure 50, 
consisting of greenhouse, indoor and outdoor concrete pools and all acces- 
sories going to make up a modern commercial fish-breeding plant. The 
tanks are 26 inches deep on the outside surface and are not sunk into the 
ground. This avoids the expense of so much excavating and makes a 
height which ordinarily cannot be scaled by rats, snakes or frogs. Tanks 
had best be covered by frames of screening, but these will sometimes be 
warped or placed on carelessly, thereby giving these particular enemies an 
opportunity. Let us repeat that galvanized screening should be scrubbed 
with a stiff brush and water before placing over any kind of fish con- 
tainer. The acid-flux used in making galvanized wire is extremely fatal 
to fishes, and unless precaution is taken, the first rain on new screening 
will wash the free acid among the fishes and cause wholesale deaths. 
Uniform size of compartments has several advantages, among which is 
interchangeability of screens or covers. Allowing 6 inches for the thick- 
ness of bottom will leave an inside depth of 20 inches, but under ordinary 
circumstances they should not be filled beyond 14 to 15 inches. With the 
outside tanks this gives a safety margin of several inches before a heavy 
downpour of rain causes the level to rise to the screened safety overflows 
one inch from the top. It also catches practically all of the rainwater of 
the season, which is excellent for the fishes. If the water becomes high it 
can be siphoned off from the bottom until original level is reached. The 
advantage of being able to fill up, if necessary, to 19 or 20 inches in an 
inside tank is that at certain seasons the greenhouse capacity for fishes is 
