Aug 3, 2009, 7:55 AM
Post #1 of 84
Dissolved Oxygen: Do we need aeration during Daytime?
Wanted to share with you something aquaculture people (farmers raising prawns, tilapia, sea bass etc) take utmost care when looking after their farmed fishes - esp on Dissolved Oxygen. Normally, Dissolved oxygen concentration in ponds fluctuates on a 24-hour basis. This fluctuation is called a diurnal oxygen cycle. Dissolved oxygen increases during daylight hours when photosynthesis is occurring and decreases at night when respiration continues but photosynthesis does not.
Ive seen posts where people claim that they reduce their 'water pump at night to save electricity' and the like and I guess the reason for this post is to actually warn against this practice especially if the pump agitates the water to help produce DO.
Ive also seen many filters that continuously run aerators during the day and IMO, this can be reduced as there simply is a lot of Oxygen circulating around. BUT this is a big requirement at night to keep the bacteria & the fish alive.
In fact one posts Ive read fr the Phils (Pond Disaster (All My Koi's Died)), said it all, the fish kill was noted in early morning after all the pupms was accidentally turned off.
I would encourage members who have DO equipment to validate this by testing at different times of the day (ie 6am, 12 noon, 6pm, 12 midnight).
However, there are situations where DO in the morning decreases like, very hot weather (>34 C), overcast skies/no wind.
Ive attached a table to show the day-night-day-night (dndn) effect to DO levels.