Well, the water will be rich in Oxigen that way. But morever, the water absorbs oxigen in the air the MOST when it is exposed in the air, so it's ok without an air pump (I don't have one) but as the water is pulled up to the filtering housing, you should ****let the it spread out in a large surface and let the covering open so that the water will be exposed the best!
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~Nam Nguyen~
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