OPACITY OF THE TANK. 371 



dimness in the water, much future trouble will be 

 saved. 



Supposing the water to have become opaque, 

 proceed thus Draw off a portion into a large jug, 

 and mix with it the diluted acid as before stated, 

 then let the jug remain undisturbed for about twelve 

 hours. The vegetation having been deposited in 

 flakes at the base of the vessel, the water should then 

 be gently strained off through a piece of fine muslin 

 into a second receptacle, which, in its turn, should be 

 allowed to stand for some time, and the contents 

 again strained as before. This process it is advisable 

 to repeat several times, until the whole of the fluid 

 in the tank has been thoroughly cleansed from im- 

 purity. 



Should the water be returned too early, an un- 

 pleasant fur coating will appear over the entire base 

 of the tank. This can be easily removed by means 

 of the siphon. Let one end of this instrument, 

 when in action, be passed gradually over the lower 

 portion of the vase, and in the course of a few minutes 

 every sign of ' fur' will be obliterated with the loss 

 of but a small portion of water. When once the 

 fluid has been clarified in the manner here men- 

 tioned, there is little fear of the young aquarianist 

 being again troubled in like manner for many 

 months, the acid apparently preventing the algae from 

 being reproduced to any such excess as hitherto. 



