THE AQUARIUM 77 



case a more or less elaborate rockwork will require to be built 

 up according to the taste of the owner. 



The Freshwater Aquarium. If we begin with the freshwater 

 aquarium, the first thing is to obtain clean sand, taken from 

 a river or stream by preference. Sea sand should be avoided, 

 as it is difficult to remove all the salt, which would be fatal to 

 the future inhabitants. The sand in any case should be very 

 thoroughly washed, and spread over the bottom to the depth of 

 an inch or two. The next point is to select water plants. Some 

 of these, like the Canadian waterweed, will do quite well if a few 

 branches are simply thrown into the water, others, like water- 

 crowfoot, and some of the pondweeds, require to have their roots 

 fixed in the sand. These should be taken up as carefully as 

 possible, and then planted in the aquarium. After this is done 

 sprinkle a layer of well-washed gravel on top of the sand, especi- 

 ally about the roots of the plants, to prevent these being dis- 

 turbed when the water is poured in. It will be well also to 

 have some larger stones, of irregular shape, so arranged that 

 those animals which do not live always submerged can raise 

 themselves temporarily above the surface of the water. This 

 is especially necessary if aquatic larvae, such as tadpoles or 

 insect larvae, are to be kept. The next point is to introduce 

 the water as gently as possible. This may be done with a water- 

 ing pot furnished with a fine rose, or by means of a bent-glass 

 tube used as a siphon. The water should be perfectly clear as 

 soon as the coarser particles have settled, and the whole should 

 be left for some days, at any rate, before any animals are intro- 

 duced, to make sure that all is going well. If the water of the 

 locality is known to be specially hard, tap-water should not be 

 used, but instead that taken from a clean rain-barrel. Many 

 recommend this in any case as an essential for success, but it 

 often happens that the only rain-water available is too foul to 

 be utilised. In this case tap-water must be employed, but it 

 should be noticed that very hard water is a poison to many fresh- 

 water animals. 



After the tank containing its plants has been left for some 

 days, and all is seen to be going well, the animals may be intro- 



