CONDITIONS OF LIGHT, ETC. 



The odor of the water is also a means of determining its condition, as 

 when this is strong, vitiation has advanced to a dangerous degree, and to 

 keep the inmates alive it is not only necessary to entirely refill the aquarium 

 but it should be cleaned, the plants reset, and after a few days the water 

 again changed. Experienced aquariists can tell the condition of the water 

 by its taste. 



When the conditions are good there is no need of changing the water 

 for long periods, as filling in what has evaporated is sufficient, or remov- 

 ing a part of the lower depth and adding a little fresh water, from time to 

 time, especially when the weather has became warmer. 



The aquarium should have a considerable change of water, more than 

 half, when hot weather sets in, and it may be advisable to change part of 

 the water occasionally, say once a month, if not perfectly clear. The new 

 water also brings into the aquarium some of the mineral salts necessary 

 for the plants and animals, which may become exhausted by longstanding. 

 Culturists of the food fishes recognize the benefit of occasionally turbid 

 water, as the precipitation of the particles of soil act as a disinfectant, and 

 the mineral substances are required by the fishes to digest their food. In 

 ponds and streams, rainstorms will supply this requirement, but at the 

 beginning of the feeding period of the alevin, breeders of the trout and 

 other food fishes make the water of indoor hatching basins thoroughly 

 turbid twice a day by pouring into it a mixture of water and rich sod soil, 

 after which the young fishes take their food with particular readiness. 

 The breeder of the goldfish supplies the required mineral constituents by 

 placing dishes of turf in the rearing tanks, which is especially necessary to 

 furnish soil artificially in wooden tanks and cement basins, as otherwise 

 the health and growth of the fishes will be impaired. Muddy water is a 

 favorable remedy for some of the illnesses of goldfishes and is frequently 

 used. A small piece, of plaster of paris is also beneficial, as it furnishes 

 lime to the animal inmates. 



Dr. W. Koch demonstrated that the addition of like quantities of 

 nitrate of ammonia and biphosphate of potassium with a minute quantity 

 of iron to calciferous wellwater, in which a number of water plants were 

 placed, soon produced very green and turbid water rich in plant life 

 consisting principally of algas, voucheria and wolffia, when kept at a 

 temperature of 50° to 54^ F. This admixture produced conditions favor- 

 able to the development of the ever present spores of these low plant 

 forms, which are beneficial to the animals in the aquarium. 



When much animal life is present in proportion to the size of the 

 aquarium and the plant growth is insufficient, frequent changes of water 

 are necessary. In overstocked aquaria this must be done daily, but 



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