Mix, when wanted, to consistency of stiff putty, with raw linseed oil.
After reading all these directions and getting the idea of an aquarium, one should think the whole matter out for himself and make it just as he wants it. Directions are useful as suggestions only. The shallow form is better for raising toads, frogs and insect larvæ; the deeper aquaria show water plants and fishes to better advantage.
Inhabitants of the Aquarium.
Fig. 60. Eel-grass.
It is now time to begin to think about what shall be kept in the aquarium. At the bottom a layer of sand, the cleaner the better, two or three inches deep will be needed. A few stones, not too large, may be dropped in on top of this first layer, to make it more natural. The water plants come next and will thrive best if planted securely in the sand. The most difficult thing is to get the water in without stirring things up. A good way is to pour the water in a slow stream against the inside of the aquarium. The best way is to use a rubber tube siphon, but even then the water ought not to flow from a very great height. If the aquarium is large, it had better be put in its permanent place before filling.
The aquarium will soon be ready for snails, polliwogs, and what ever else we may wish to put into it. In the course of a few days the plants will be giving up oxygen and asking for carbon dioxid.
Fig. 61. Duck-weed.
Plants that thrive and are useful in aquaria.—Many of the common marsh or pond plants are suitable. The accompanying illustrations show a few of these. Nothing can be prettier than some of these soft, delicate plants in the water. The eel-grass, or tape grass ([Fig. 60]), is an interesting study in itself, especially at blossoming time when the spiral stems, bearing flowers, appear.