The Book of the Aquarium/Part 2/Chapter 1
THE BOOK OF THE AQUARIUM.
THE MARINE TANK.
CHAPTER I.
THE VESSEL.
Points in which the Marine differs from the River Tank.—Though vessels of precisely the same construction are used for marine as well as fresh-water aquaria, yet, as the peculiar necessities of marine life demand some conditions of a special kind, I must here again briefly treat of the vessels in which marine stock may best be kept. Every variety of tank or vase referred to in the description of the fresh-water aquarium may be used in the formation of marine collections; but while vases are eminently suitable for river stock, they are not to be strongly recommended for marine, and for this important reason, that we do not generally have, as in the former case, a variety of moving forms poising in midwater, or chasing each other through every part of the tank but in the present case ground stock constitutes the main feature of attraction, and hence we require a vessel which admits of examination in every part, which a tank does and a vase does not. In a vessel containing actinia, madrepores, serpula, &c., we require to have at all times a clear view of the bottom, and a vase does not admit of this unless we look from above, the amount of refraction being very great at the base of the vessel. Hence, though marine stock may be well kept in vases, it must be borne in mind that such vessels are far inferior as to the means of inspection to rectangular tanks.
It is also important to bear in mind that marine stock invites the use of the microscope in a greater degree than river specimens, and a flat-sided vessel is the only one which affords proper facilities for the application of a magnifier to its contents.
Stained Glass.—But there is a still more important matter requiring notice here. We are indebted to that accurate observer, Mr. Warington, for valuable information on the effects of light upon certain forms of sea weeds, and his mode of overcoming this is by passing light through variously coloured media. It can easily be understood, that plants, whose natural habitat is at a considerable depth beneath the surface of the ocean, bear exposure to the full daylight very indifferently, and that some special arrangements are necessary in order to cause the solar rays to fall upon them as nearly as possible in the same manner as in the twilight recesses from which they have been removed. This is accomplished by fitting that side of the tank, which is intended to be placed next the window, with a sheet of glass stained of a soft sea green, and the softened light, so admitted to the tanks, promotes the healthy growth of the Algæ, and very materially increases the beauty of the vessel as seen from the other side. Mr. Lloyd, whose ripe experience ever takes the most practical turn, has adopted this plan of construction, and strongly recommends it for every vessel intended for the reception of marine stock. Where it is desired to stock a vessel, in which the back plate is composed of colourless glass, with marine products, a substitute for coloured glass will be found in diaphanie; but the paper chosen for the purpose should be of the lightest shade of sea green, because it is less transparent than stained glass. In stocking vases, this plan of staining the side, next the window, is to be strongly recommended, no less for securing a healthy vegetation than of enlivening the beauty of the collection. I have used for this purpose, the paper and varnish prepared by Messrs. Faudel and Phillips, of Newgate Street, and can commend it for cheapness, and the ease with which it can be applied.
Another point deserving, of note is, that marine aquaria need a less depth of water than river collections:—For purposes of study, a number of glass dishes or milk-pans, will be found preferable to any kind of tank, or vase, especially for Zoophytes, though fishes and crustaceans require more room than mere bowls would afford them. In fact, the lower forms of marine life may be kept for many months without the help of sea weeds, if placed in shallow vessels—the absorption of oxygen, at the surface, being quite equal to their demand upon the water.
In all other respects, what has been already said on the subject of vessels must be understood to apply to all kinds of aquaria; the rectangular tank, and the bell glass, are the two leading forms, and to them I shall always refer when speaking of the tank in a general sense.