Tanks for Marine Aquaria. 
241 
give it up, and provide yourself with one of proper make and character. These 
shallow vessels, made expressly for beginners, may be imitated in an expensive 
way by means of a glass dish, an earthenware foot-bath, or any other vessel 
not metallic, of similar form and dimensions. 
The very best and cheapest ready-made vessel in which to preserve a few 
sea anemones is a glass dish, such as is used in dairies for cream, or the 
glass which forms the lower half of a common fern-shade, as here 
figured. 
From this simplest of all forms of vessels, let us proceed another step. 
The tanks with four sides of glass admit a vast deal too much light, which 
is not only injurious to marine animals, but causes the vegetation to become 
rampant and unmanageable. Instead of a velvet-like growth of minute 
Alga on the rock-work, involved ropes of Conferva appear, or, what is 
worse, the water becomes opaque with “green stuffthere are more 
spores set free than can find resting- 
places, and they float in the liquid) 
and make it of the consistence of 
pea-soup. Light alone must not 
have all the blame, for heat is also 
a powerful agent to bring about 
such a state of things. It is evident, 
therefore, that the heavier the vessel 
is in bulk, proportioned to its size, 
the more slowly will it be affected 
by heat; a heavy non-conducting opaque material should largely predominate 
in the construction of the tank, and nothing has hitherto been found so suit¬ 
able as slate. The lighter and more fully illuminated the vessel, the less is 
its value for marine purposes; it must be heavy, and but partially open 
to the effect of light, and then an equable temperature is obtained, and 
a more constantly pellucid state of water. Mr. Warrington’s name must 
have honourable mention here, as the inventor of the slope-back tank, 
which realizes the conditions of success more completely than has been 
accomplished by any and every other means. 
The object sought to be accomplished by this form of vessel is a closer 
imitation of the conditions under which marine animals exist in their 
native waters. There the light which reaches them is wholly vertical, or 
at least the laterally-refracted rays are but of small account. In the 
CIRCULAR GLASS ROCK-POOL TANK. 
