FISH DISEASES 95 



Last Resorts. Occasionally someone tells us that they have con- 

 scientiously followed every direction in our book and yet their fishes 

 seem droopy and listless, or perhaps they are dying. Unusual microscopic 

 and chemical conditions arise in water at different locations which are 

 difficult to analyze, especially from a distance. Usually they are only 

 temporary. 



A good plan in such cases is to give the fishes a complete change into 

 other water which has been boiled, cooled and aerated. This eliminates 

 bacteria or chlorine. As elsewhere stated, it is also a good idea to take 

 water directly from a stream or pond known to contain fishes. A change 

 of diet to chopped earthworms is a further help, or, if they are not avail- 

 able, to one of the animal foods mentioned in the chapter on "Fishfoods." 

 Finally one should take another sharp look for ichthyophthirius or other 

 disease, and also check up on the air-surface-per-fish rule, if goldfish are 

 being considered. 



No air-surface rule has been worked out for tropicals because of 

 their infinite variety, and while most of them can stand close quarters, 

 they surely would enjoy getting into an aquarium where they can stretch 

 their legs! 



Acid-Alkali Tests. Modern research has definitely established 

 the fact that many forms of life are vitally affected by acid or alkaline 

 environment, the two being of opposite qualities, like positive and nega- 

 tive electricity. Vegetation and lower aquatic animal life are often 

 keenly susceptible to these conditions, particularly in the matter of re- 

 producing themselves. It is, therefore, our interesting problem to find 

 the condition which will be unfavorable to fish enemies without harming 

 the fishes. Simple and inexpensive testing sets are now available to 

 aquarists, and in use by many of them, not only for the control of 

 disease, but also in establishing favorable breeding conditions for the 

 different species. Much has yet to be learned in this field, but it appears 

 to be well worth delving into. 



On the scale accompanying these sets (called pH or hydrogen ion 

 sets) the neutral point is at 7. All above is alkaline, and below is acid. 

 The accepted safe range for aquarium fishes is between 6.4 and 7.4. 

 Water kept at about 6.8 is suited to most aquarium fishes and is un- 

 favorable to many bacterial and parasitic enemies and to micro vegetal 

 organisms which cloud the water or turn it green. 



Under control of a test set there are several acids which are safe 

 to use. Among them are hydrochloric, acetic and acid sodium phos- 

 phate, the latter being preferable, as well as more permanent in its 

 effect. The simplest agents for turning water to the alkaline side are 

 bicarbonate of soda (washing soda) or lime water. 



