Fish enemies are usually transferred to the aquarium by the introduction
of new aquatic plants that are obtained from outside pools. To avoid
fish enemies—AVOID USING PLANTS AND SAND THAT ARE OBTAINED FROM OUTSIDE
POOLS OR PONDS. If you are suspicious of source rinse for a minute or
two through a strong solution of salt water. This should kill all
insects and not injure plants. Examine plants carefully for eggs. Fig. 6
shows larvae of Giant Beetle (Water Tiger). Fig. 7, larvae of Dragon
Fly. Both attack fairly large fish and devour small ones in quantities.
[Illustration: FIG·5]
[Illustration: FIG·6]
[Illustration: FIG·7]
HYDRA—a polyp, fastens itself to plants or glass. It has a variety of
shapes and is hard to distinguish particularly on plants. It attacks and
quickly drugs fish by injecting a poison. Hydra can be killed by
removing all fish and scavengers and raising temperature of tank to 115°
F.