THE AUSTRALIAN NATURALIST. 
Thereby we are creating what is termed a balance between ~ 
plant and animal life, a continual exchange taking place. Per- 
sonally I do not hold with the use of the term “balance,” which 
is so frequently mentioned in this respect. A tank thickly grown 
with plants produce oxygen far in excess to what would be re- 
quired, far beyond what would be a balance, and under these . 
conditions: our fish do all the better. : 
‘The wasting of the body is made good by the taking of food, 
which also induces growth. Food is taken as a fuel to keep the 
temperature of the blood up, but a fish, being cold-blooded, re- 
quires very little food indeed. 
What is a cold-blooded animal? A cold-blooded animal 1s one 
that assumes the temperature of the water or air in which it 
lives. Thus the body temperature of a fish in an aquarium 
is always the same as that of the water: Normally healthy, 
warm-blooded animals have a stable temperature that does not | 
vary with external conditions. 
Great care must be taken if changing of the water is re- 
quired, as the water supplied is varely of the same tempera- 
ture as that taken’ away, and if colder, the fish are apt to take a 
chill; if; warmer has a disturbing effect on the slimy matter~ 
which covers the whole body of a healthy fish. Again, in remov- 
ing and handling a fish, it is apt to receive injury, such as an 
mjury to or the total loss‘of a scale. ; 
Now all waters contain parasitic organisms, either ‘animal or 
vegetable, awaiting an opportunity to attack fish-life, from 
which they then draw their nourishment at the expense of the 
fish Tf the fish are in a healthy condition they are not likely 
‘to be attacked; if the fish has an-injury or the body-coating not 
performing its function, these parasites immediately settle on. 
the weak spot and inerease at an alarming rate, and ten to one 
it is a case with your fish. Successful treatment in such cases 
is possible if taken in hand at once; it is always troublesome, 
and only worth while with valuable specimens. Thus should 
there be any need to change the water, always see that it is of 
the same temperature. Prevention is easier than cure. 
‘The greatest of care must. be observed with newly-aequired — 
fish, which under no circumstances should be placed with others. 
These should always be quarantined for a week or two, to avoid 
risk of introducing disease. All fish which I have received from . 
the various parts of America are remarkably free, but every 
one from the East requires yery careful watching. Our own 
