36 
THE FRESH-WATER AQUARIUM. 
which arises from to much sun is this: that the small green plants 
of conferva grow very rapidly upon the glass and stones, obstruct¬ 
ing the view of the inside of the tank, and rendering the stones 
very hard to clean when taken out. These confervse do not injure 
the water at all; they even give out oxygen as other plants, and 
it seems as if it were a provision of nature, that they should ren¬ 
der the glass opaque so as to protect the inmates of the tank from 
injury. This confervoid growth is not essential to the welfare of 
the tank if it is properly stocked with other plants, and it is de¬ 
sirable to have as little as possible of it. To effect this, a wide 
screen, or a simple sheet of brown paper, so placed as to shut out 
the sunlight from the tank will answer the purpose ; or by pulling 
the window shade down when the sun shines upon the tank; or, 
what is best, by placing a row of plants with full foliage between 
the tank and the window, we have other means of obviating the 
difficulty. 
Whether the sun shines upon the tank or not, a fresh-water aqua¬ 
rium should have all the daylight it can get, both for its own 
welfare and our own convenience in examination. I am convinced 
that this is correct from my own experience, although Mr. Hibberd, 
a good authority on aquarial matters, says to the contrary : “A 
full flood of daylight does more harm than good, a frequency of 
sunshine is destructive, and the tenants of an aquarium are seen 
to better advantage in a vessel lighted from above only.” Before 
any specimens are introduced into the tank, it should be thorough¬ 
ly washed out and the glass cleaned on all sides, as this is the 
onty time when it can be done to advantage. We are sure then 
that no impurity of any kind will thus far hinder the success of 
the aquarium. The tank then is ready for the rock-work. This 
rock-work is useful: first, as a shelter for the animals, some of 
them being averse to the light if it is strong ; second, as a means 
of concealing the sediment which, without doing any material in¬ 
jury, so mars the beauty of an aquarium ; third, as a means for 
anchoring in their proper place the plants we put in ; fourth, and 
lastly, to make the effect of the aquarium more like nature. 
It is generally thought that most water-plants, to do well in an 
aquarium, must have soil to grow in as well as land-plants, and 
that a layer of earth or sand must be spread over the bottom of 
the tank for the roots ; this is found by experience to be a mistake. 
No earth or sand is required for the plants which grow best in the 
