396 



THE GUIDE TO NATURE. 



it is not essential if the knots are solid 

 and tight. 



Spruce and Hemlock can be used 

 when there is no liklihood of the water 

 ever being emptied, and it is surpris- 

 ing how long both will last. But as 

 they ought not to be allowed to dry 

 out they are not convenient. 



There is some diversity of opinion 

 to fishes; but the majority idea seems 

 to be that sheet zinc is not injurious 

 to either plant or animal life, and that 

 properly supported boxes made of it 

 will give good tanks. With the re- 

 quired bracing they will weigh about 

 the same as wooden tanks of similar 

 size, and they have the advantage that 

 they can be emptied and filled at pleas- 

 ure without even the small leaks that 

 always occur when a wooden tank is 

 refilled. It has the objection that neither 

 confervae or algae readily grow on the 

 surface of the zinc or, if they grow at 

 all, some condition generally causes 

 them to become brown and die early. 



Both cast and rolled iron tanks are 

 obtainable, and no doubt if properly 

 covered with a protective varnish will 

 do quite well. Asphaltum, spar and 

 boiled oil varnishes are probably the 

 only ones that will prove satisfactory. 

 These tanks are rather objectionable 

 for the following reasons : first, they 

 are quite heavy ; secondly, if much rust 

 is present the plants suffer; thirdly, 

 to avoid rust constant attention is re- 

 quired in varnishing; fourthly, the 

 algae will not attach itself to the freshly 

 varnished surfaces. Notwithstanding 

 all these objections they have been used 

 with success. 



Both slate and soapstone make ex- 

 cellent tanks as far as the healthful con- 

 dition of plants and fishes are con- 

 cerned. They both, however, have the 

 very serious objections of great weight 

 and (unless obtained second hand) 

 considerable original expense. Other- 

 wise beyond question they make the 

 best tanks for out of doors ; the soap- 

 stone probably being the better one, 

 if choice exists. 



Galvanized iron should never be used. 

 Depending upon the newness of the 

 receptacle, large or small quantities of 

 hydrochloric acid, chloride of zinc and 

 other chemicals are always present; an 



entirely new vessel will kill all the 

 fishes in a few hours and destroy the 

 plants. The same comment applies to 

 galvanized wire netting and it should 

 not be made use of until it has been 

 well seasoned by exposure to the 

 weather. I have known all the fishes 

 in a tank to be killed in one night by 

 the rain washing through a new galvan- 

 ized wire screen that had been put 

 over to protect from some cats that 

 were plundering. 



Copper is another material that must 

 not be used unless well tinned and 

 again over that a coat of spar varnish. 

 There is, however, always a doubt and 

 it is better to avoid it altogether. 



A tank even more than an aquarium 

 should have a good surface of water 

 exposed to the atmosphere, not only 

 for aeration but also to enable light to 

 reach the plants. Of necessity shal- 

 low boxes will have ample surface area, 

 but the generally accepted design for 

 deep tanks makes them too narrow ; 

 whereas the width should be at least 

 one-third greater than the depth and 

 better yet if twice as much. In other 

 respects the form of a tank is entirely 

 a matter of convenience. 



A zinc tank is merely a box made 

 of sheet zinc soldered together, with 

 a protecting crate of wood, and it ought 

 not to have a surface area greater than 

 six square feet nor a depth of more 

 than fourteen inches. The crate should 

 fit tightly, having a nearly solid bottom 

 with side strips at the top and bottom 

 connected at the corners. The zinc 

 box having been settled on the bottom 

 of the crate, the free upper edge of 

 the zinc is turned over on the edge of 

 the top wooden strips and tacked fast. 

 As there is very little strain on the 

 crate it can be made of light wood. 



Stone tanks are of slabs of a thick- 

 ness proportionate to the strength of 

 the material. They are put together 

 with screw bolts, the thread of the 

 bolt engaging with a burr that is leaded 

 fast in the opposing slab. White lead 

 or other cementing material is used 

 at the joints. 



Cast and rolled iron tanks, like the 

 last, will not likely be attempted by the 

 amateur and no further notice of them 

 need be made. 



