EECEEATIVE SCIENCE. 



75 



minnows vrere dead also, but one or two of 

 them survived, and at a sad price I learnt one 

 more lesson as to the effects of light upon 

 aquaria. A powerful sunshine in a room 

 wUl, of course, not be so dangerous as on a 

 wooden bench between two hot walls ; but it 

 is a question of degree only, and whoever 

 desires to see a beautiful collection of river 

 plants and animals, must be prepared to shut 

 out excess of light if the position of the vessel 

 be such as to admit it. Many readers will, 

 doubtless, be surprised when I assure them 

 that the vegetation ordinarily used in river 

 tanks is altogether unsuitable. If tanks are 

 to be managed on the self-supporting prin- 

 ciple, away with the flowering rushes and 

 water violets, water milfoil, and all the tribe 

 of NymphcBa, and trust for the supply of 

 oxygen to the spontaneously produced vege- 

 tation, of which there will be plenty, if the 

 foolish system of scrubbing and cleaning and 

 changing the water be given up. Once a-y ear 

 is often enough to change the water, and it 

 only needs to be changed then in order to 

 lay down fresh pebbles in the place of those 

 which have become black, and to make such 

 other changes as taste may suggest, for 

 variety's sake. The majority of aquatic 

 plants do well only for a time. After awhile 

 they rot at the base, and float away from 

 their moorings, or get so sickly for want of 

 deep soil to root in, and hot sunshine to sti- 

 mulate their growth, as to be a nuisance. 

 Exceptions may be made in favour of Valis- 

 neria spiralis, the best of all aquarium plants ; 

 Anacharis alsinastrum, which will thrive 

 under the most trying of circumstances ; 

 Stratiotes aloides, which floats about, grows 

 well in a subdued light, and occasionally 

 anchors itself by means of its long cord-like 

 roots ; Hydrocharis morsus-ranct, which floats 

 on the surface, and does weU in most posi- 

 tions ; and the three Lemnas, minor, trisulca, 

 and polyrJiiza. Anj of these may be per- 

 manently planted, and it will be very excep- 

 tional indeed if they do not prosper, espe- 



cially if there are no Lymnea, which are very 

 destructive. With the exception of these, 

 trust to the Confervce, the Oscillatoriew, Vau- 

 cheria ungeri, and other low forms of vege- 

 tation, which come in their own way in every 

 tank which is left undisturbed, and there will 

 be plenty of surface for them to rejoice upon 

 if only the front plate be kept clean, by 

 means of a sponge attached to a stick. 



This proscription of the very plants which 

 have been considered the most attractive fea- 

 tures of the aquarium may create surprise. 

 Let not the surprise be changed to fear ; you 

 may have them all, and many other beautiful 

 aquatics, if you take care not to plant them. 

 I use a very large variety of British and 

 exotic plants as tank decorations, and amongst 

 the number of my favourites are ferns. The 

 cut at the head of this article represents a 

 tank which I lately fitted expressly as a water 

 fernery, and it accomplishes all that can be 

 desired as a decorative object without vio- 

 lating any principle of aquarium philosophy. 

 Instead of planting in the aquarium, pot 

 plants only are used. They are grown ex- 

 pressly for the purpose, and may be changed 

 as often as the extent of the stock of plants 

 wUl aUow, so as to vary the scene with the 

 changes of the seasons. 



To carry out this scheme all that is ne- 

 cessary is to model a rockery to the shape of 

 the tank. But it should not be fixed, for it 

 may be desirable to remove the whole or 

 part of it at some time or other, for the pur- 

 pose of effecting a change in the decorations. 

 Use pumice-stone or coke. If the latter, dip 

 it twice in a batter of Portland, as lately 

 advised by Mr. Noteworthy, and you will 

 secure the desiderat\am of a substantial and 

 handsome rockery, weighing only a few 

 pounds instead of two or three hundred 

 weight. In the tank, which forms the sub- 

 ject of illustration, the rock-work consists 

 of a series of arches, bearing eight sum- 

 mits, to correspond with the eight sides 

 of the vessel, the whole resting on four shafts 



