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 iish 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. 



As 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 w-ater-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, w^hich 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 



