Missouri Botanical 
Garden Bulletin 
Vol. VII St. Louis, Mo., June, 1919 No. 6 
AQUARIUM EXHIBIT 
Through the instrumentality of the St. Louis Aquarium 
Society, the Garden is fortunate in being able to establish a 
display of fancy fish, exhibited in specially prepared eS 
which have been installed in the alcoves of the aroid house. 
The attractive rockwork around the aquaria eliminates the 
artificiality generally associated with such displays. An 
additional feature of the exhibit is the use of various aquatic 
plants suitable for aquaria. Such plants are indispensable 
for maintaining the life of the fish, possessing ihe power of 
generating oxygen. Pure oxygen is essential for fish, while 
carbon dioxide is a plant necessity; thus a balance is main- 
tained, the oxygen given off by the plants being utilized by 
the fish, while the carbon dioxide exhaled by the fish is ab- 
sorbed by the plants. Without this reciprocal relation it 
is impossible to attempt fish culture successfully. It has been 
repeatedly demonstrated by specialists that aquaria contain- 
ing sufficient plant life may be tightly covered, the plants 
giving off enough oxygen to support a proportionate number 
of fish. The feces excreted by the fish are absorbed by the 
plant roots as food. : 
The ornamental value of plants in aquaria is another im- 
portant feature. The plants used may be either native or 
tropical, placing stress upon those which possess to the larg- 
est degree oxygen-generating properties. The best plants 
for this purpose are: pond-weed (Potamogeton crispus) , fish- 
grass (Cabomba caroliniana), eel-grass ( Vallisneria spiralis) , 
water-weed (Elodea canadensis), and ribbon arrowhead 
(Sagittaria subulata). 
Pond-weed (Potamogeton crispus)—A native of Europe, 
forming greenish brown growths. The leaves are lanceolate 
with undulated margins and the flowers white. One of the 
best oxygen generators, but an exceedingly noxious weed in 
outside ponds. 
Fish-grass (Cabomba caroliniana).—A native of North 
America. The green leaves are produced in fan-shaped for- 
mation from the central stem which reaches a length of four 
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