Day Vs Night water movement

In our natural reefs, water movement slow down at night time to a tranquil state. Now as for flow in our aquariums, it is a much smaller scale and for us with a deep sand bed, oxygen depeltion happens at a much quicker rate than for those that don't have a deep sand bed. Bacteria and other living animals in the benthic areas of our tanks use up the available dissolved oxygen at an alarming rate through respiration. Plus the fact that photosynthesis has ceases once the lights have turned off, you have two means of rectifying this:
1) create a reverse daylight scenario on your refugiums or sumps housing macroalgae.
2)adjust your powerheads(don't have to maintain intense flow or add flow at night) to create turbulence at the air/surface interface. This will enable a good gas transfer as dissolved carbon dioxide is removed, beneficial oxygen will replace it!

 

Really? who woudda thunk....

;D