FOOD FOR FISHES. 47 



earth worms. Whether they will accept them or not 

 depends upon their capricious humour, and if they are 

 not eaten they only accumulate on the bottom and foul 

 the water. A much better plan is to keep as many 

 snails as you possibly can. Their spawn is a favourite 

 food with fish, and what with that, animalculae, ento- 

 mostraca, and the fresh shoots of aquatic plants, they 

 manage to make all the feeding they require. If fresh- 

 water animals have to be artificially fed the best diet 

 is the blood- worm (Tubifexrivuloruin), which is to be 

 found in many ponds and streams. Many fish eat it 

 greedily, and it has the advantage of being an aquatic 

 worm, so that if it be not eaten at the time you put it 

 in the tank, it lives to be eaten another day ! The 

 fine blood-red colour of this worm is due to the false- 

 blood being visible through the thin skin. 



We have seen that the gradual change of the water 

 to a greenish hue is due to the presence of minute 

 vegetation which the undue light has stimulated into 

 existence, and that the remedy for this was to sub- 

 due the light until the evil was overcome. Now we 

 have to notice another unhealthy condition of things 

 to which the inhabitants of a fresh-water tank are 

 liable. Occasionally the weeds are covered with a 

 white hairy slime, and the water gets thick with a 

 muddiness which is evidently due to the same cause 

 as the condition of the plants. Perhaps you will also 

 notice the fishes gasping on the surface, as if they 

 were unwilling to breathe the foul air mixed with the 



