Increasing Dissolved Oxygen In Aquarium. Plants are one of the major sources for improving dissolved oxygen in natural water bodies. Skimmer and large circulation pump removed at 8:15 am (circulation pump replaced with a smaller unit.) temperature fell by 1.44 f over the next 1.5 hours (due to removal of two 'warm' pumps.) dissolved oxygen dropped also, by 0.32 ppm.
The speed of gases exchange between the water, also in the air increases when water distributes on the surface of storage tank. The newly agitated water will introduce more oxygen to the aquarium, while the increased water movement will improve the oxygen exchange, buying some time to address the underlying cause. Fish absorb the do directly from the water into their bloodstream through their gills.