Pottsy is correct. The tank with the light green tint contained lots of oxygenating microalgae. Microalgae (attached & suspended) can produce lots of oxygen IF there is sufficient light. Without sufficient light they can do the opposite and CONSUME oxygen. Also if they die or are KILLED the tremendous bacterial bloom that quickly develops to decay the microalgae consumes even more oxygen than the microalgae did.

AN ADDED NOTE ABOUT HIS PHYTOPLANKTON SAMPLE DESCRIBED ABOVE. His water clarity or visibility was about 4 feet. Think how many more microalgae will be in water with clarity of 12" to 24"!


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