TROPICAL AQITARIIT:\[ FISHES U 



aquarium. As the air passes through tlie water there is sufficient oxygen 

 absorbed to keep the fish always in good condition. This is also very 

 helpful to the fish at night. 



There are many varieties of pumps that can be used for this purpose, 

 but the cheapest and most satisfactory are those which are operated by 

 water power. The type known as "beer pumps" are the best. These oper- 

 ate on a very simple principle, having a minimum of working parts and 

 therefore little to get out or order. Air is forced out of an air-chamber 

 by the entrance of water. When the air is all expelled, an internal float 

 stops the supply of water and starts a siphon working which empties the 

 pump preparatory to the next filling. As this operation takes about a 

 minute it is advisable to have a small storage tank for the air to pass 

 through in order to equalize the flow. A very small stream of air run- 

 ning through the aquarium will keep the water sweet even though the 

 aquarium is somewhat overcrowded. Overcrowding, however, is not to 

 be encouraged at any time. 



The air should be liberated in as small bubbles as possible. Libera- 

 tors are made especially for this purpose, but a good home-made plan is to 

 place a piece of bass wood or other open grained wood in the end of a 

 tube to force the air through it. In case the liberator becomes clogged up, 

 allow it to dry out for a day or two. 



An air pump may also be used to operate a filter for the aquarium 

 or to make a fountain without the use of water other than that already 

 in the aquarium. (See Chapter on Aquarium Appliances.) 



Scavengers. Xature has supplied us with means of getting rid of 

 most of the harmful offal and decomposition in the aquarium. These con- 



FiG. 2. African Fig. 3. Japanese Ph.. 4. Red Ramshorn 



The Three Best Freshwater Aquarium Snails {Life size) 



sist largely of those species of snails that do not attack the plants. Among 

 the best known, most satisfactory and easily obtained are the large Japan- 

 ese snails {Viviparous mallcatns), the so-called African paper shelled 



