Originally Posted By: catmandoo
....For the 10 gallon tanks I have some inexpensive Wally-World air-stones that stretch nearly edge-to-edge lengthwise in the aquariums. They are placed at the very bottom of the tanks where they are nearly covered with gravel. ......


I wonder if the nearly covering the air stones in the pea gravel has set up a bio filter of sorts with bacteria collecting on the gravel....

Under gravel filters work that way although they usually have small activated charcoal pods on the out flow tubes.

Last edited by Bill D.; 12/30/15 08:21 PM. Reason: Clarification
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