96 THE MARINE AQUARIUM. 
bubbles of sulphuretted hydrogen upon their bodies, and 
they should be removed before this spreads and devastates 
the tank. 
Removal of Objects.—For the removal of portions of 
decayed weed, and other small noxious bodies, from the 
bottom, a glass tube of 4 or § inch diameter, open at 
both ends, will be found very useful. Place a thumb or 
finger on the top of the tube, and thrust it down over the 
object to be removed, then remove the finger, and the 
matter will rise in it. Lift the tube up to the surface of 
