Pond Boss Forums AERATION Systems questions Is aeration always necessary?

Question from FishinRod "..... if you can only aerate 20% of a pond, will the fish tend to migrate from their favorite spots to the oxygenated water during a crash event? Or is the diffusion of oxygen into the depleted oxygen waters so miniscule that the fish may die while 100' away from good water?"
IMO no - the fish will not migrate with the intention to get more DO water. 1. HOw will they remember where the higher DO is? 2. I am pretty sure they cannot detect higher DO 20 ft away. I've watched fish dying and not getting enough oxygen. IMO they aimlessly swim about 'gasping' for more oxygen. 3. They might find the higher DO water but only by accident. 4. It might be possible that the water in a certain spot always has higher, thus the fish frequently visit the area with higher DO. Possible but very doubtful in my mind. 5. Oxygen diffuses very, very, very slowly in water. Currents are mainly responsible for spreading and moving the DO in water.

Question from Boondoggle - " a deep water refuge that was subject to thermoclines which basically becomes unusable in the summer months. If you were able to mix from the deep area what would happen to usable area and water temps as a result."

Let's see IF I understand the question correctly. " what happens to the surface usable zone and the water temps when you mix colder anaerobic no DO water up into the surface zone?"

For a normal bottom diffuser aeration system that rising currents of bubbles mix bottom to top, Some of this depends on how much volume of anaerobic water is mixed upward into the top layer. The anaerobic cooler water dilutes the surface water and lowers its temperature; depends on flow volume. This degrades the quality of surface water with no DO in the water and the hydrogen sulfide gas is very toxic to fish. Each factor separately can kill fish. A double wammy for fish happens who now cannot get enough oxygen and also the H2S poisons them. The cannot 'breathe' and have to deal with a poison. If the surface water is degraded enough lowering or diluting the DO and the H2S is concentration is high enough fish die.

However there are aerators called hypolimnetic aerators that mix only the deep cooler water. I wrote a term paper (grade A+) about this for graduate school limnology class. I am currently testing a new design for a guy in PA for this type of aerator to oxygenate only the cool deep zone. Also Pond boss magazine has had a couple recent articles about new versions of hypolimnetic aerators. IF you don't subscribe to PBoss magazine you should and your pond will be better for it. Editor Bob Lusk and I together have an article about stocking a new pond for the Sept-Oct PBoss mag issue.