26 THE FRESH-WATER AQUARIUM. 
covers for the jars are used at all they should be caps of 
mosquito netting held on by India-rubber rings. 
For the tank a glass rod about a foot iu length and a 
quarter of an inch in thickness will be of use in moving the 
specimens into place when disarranged. Too much cannot 
be said against unnecessarily meddling with the specimens in 
the aquarium; a slender rod with a sponge attached to the 
- end of it will be useful in removing the conferve from the 
sides of the tank; a small gauze-net three or four inches in 
diameter is often needed to remove dead or objectionable 
specimens; an India-rubber pipe several feet in length af- 
fords the simplest method of drawing off the water of the 
tank; a fine gauze should be placed over that end of the 
pipe which is in the tank, otherwise the specimens may 
pass through it and be lost. 
Should the water in the tank become impure by any means 
it can often be purified by the following simple method : take 
a small earthen flower-pot holding about a pint, and insert a 
piece of sponge tightly in the opening at the base so that 
when the water is placed in it it will pass through the sponge 
only drop by drop; the pot being filled with ici pow- 
dered chareoal and two-thirds water, place it over the tank 
and let it empty itself into the aquarium. The effect of this ' 
simple contrivance is astonishing and it will often save one 
` the trouble of arranging the aquarium anew. 
The time of edins mà the amount of food may depend 
somewhat upon the kind of stock in the aquarium. As a 
general rule it is better to keep the specimens under than 
over-fed, for they do not then by wasting their food make 
the water impure. Twice a week is often enough to feed 
them, and then very small pieces of raw beef will be found 
the best food; gold-fishes will not always eat the beef, and 
for them erumbs of bread are necessary ; should we find that 
they do not eat all that is given we must stop the feeding 
at once and remove with the glass rod the neglected portion. 
The process of accustoming certain salt-water fishes, such 
