152 THE MARINE AQUARIUM. 



house or place where the foul odor will not be trouble- 

 some and allowing the decay to go on, which it will 

 do, until all the animal and vegetable matter has gone 

 off in the form of gas and the water is left quite 

 sweet. 



Evaporation is continually going on from the water in 

 an Aquarium, but it is only from the water, the salt 

 being left behind ; and, therefore, we must replenish it 

 from the tap or spring with clear fresh water. To know 

 the exact quantity to be put in (and this is an impor- 

 tant point) we may have some mark on the glass side 

 of the vessel, as a piece of paper fastened on, or we 

 can use a hydrometer like that I have described in 

 chapter nine. 



The cloudiness of the water may be occasioned by 

 another circumstance, and that is from the increase of 

 minute animalculae ; but this ' fact need not frighten us, 

 for they arc the natural food of our fish and zoophytes, 

 who will, therefore, require the less feeding. 



These few facts will, I hope, aid the reader in the 

 proper management of a marine Aquarium. 



