Practical directions for forming an "Aquarium" may be found in Mr.
Gosse's book bearing that name， at pp. 101， 255， ET SEQ.； and those who wish to carry out the notion thoroughly， cannot do better than buy his book， and take their choice of the many different forms of vase， with rockwork， fountains， and other pretty devices which he describes.
But the many， even if they have Mr. Gosse's book， will be rather inclined to begin with a small attempt； especially as they are probably half sceptical of the possibility of keeping sea-animals inland without changing the water. A few simple directions， therefore， will not come amiss here. They shall be such as anyone can put into practice， who goes down to stay in a lodging-house at the most cockney of watering-places.
Buy at any glass-shop a cylindrical glass jar， some six inches in diameter and ten high， which will cost you from three to four shillings； wash it clean， and fill it with clean salt-water， dipped out of any pool among the rocks， only looking first to see that there is no dead fish or other evil matter in the said pool， and that no stream from the land runs into it. If you choose to take the trouble to dip up the water over a boat's side， so much the better.
So much for your vase； now to stock it.
Go down at low spring-tide to the nearest ledge of rocks， and with a hammer and chisel chip off a few pieces of stone covered with growing sea-weed. Avoid the common and coarser kinds (fuci) which cover the surface of the rocks； for they give out under water a slime which will foul your tank： but choose the more delicate species which fringe the edges of every pool at low-water mark； the pink coralline， the dark purple ragged dulse (Rhodymenia)， the Carrageen moss (Chondrus)， and above all， the commonest of all， the delicate green Ulva， which you will see growing everywhere in wrinkled fan-shaped sheets， as thin as the finest silver-paper.
The smallest bits of stone are sufficient， provided the sea-weeds have hold of them； for they have no real roots， but adhere by a small disc， deriving no nourishment from the rock， but only from the water. Take care， meanwhile， that there be as little as possible on the stone， beside the weed itself. Especially scrape off any small sponges， and see that no worms have made their twining tubes of sand among the weed-stems； if they have， drag them out； for they will surely die， and as surely spoil all by sulphuretted hydrogen， blackness， and evil smells.
Put your weeds into your tank， and settle them at the bottom； which last， some say， should be covered with a layer of pebbles： but let the beginner leave it as bare as possible； for the pebbles only tempt cross-grained annelids to crawl under them， die， and spoil all by decaying： whereas if the bottom of the vase is bare， you can see a sickly or dead inhabitant at once， and take him out (which you must do) instantly. Let your weeds stand quietly in the vase a day or two before you put in any live animals； and even then， do not put any in if the water does not appear perfectly clear： but lift out the weeds， and renew the water ere you replace them.
This is Mr. Gosse's method. But Mr. Lloyd， in his "Handbook to the Crystal Palace Aquarium，" advises that no weed should be put into the tank. "It is better，" he says， "to depend only on those which gradually and naturally appear on the rocks of the aquarium by the action of light， and which answer every chemical purpose." Ishould advise anyone intending to set up an aquarium， however small， to study what Mr. Lloyd says on this matter in pp. 17-19， and also in page 30， of his pamphlet； and also to go to the Crystal Palace Aquarium， and there see for himself the many beautiful species of sea-weeds which have appeared spontaneously in the tanks from unsuspected spores floating in the sea-water. On the other hand， Mr. Lloyd lays much stress on the necessity of a塺ating the water， by keeping it in perpetual motion； a process not easy to be carried out in small aquaria； at least to that perfection which has been attained at the Crystal Palace， where the water is kept in continual circulation by steam-power. For a jar-aquarium， it will be enough to drive fresh air through the water every day， by means of a syringe.
