Not after turnover as in thermocline but as in the water in the pond is circulated as in aeration. Common aeration produces complete pond water turnover from several times a day to several days. So you would start the diffusers at a shallow depth (5 feet) and lower the depth over a couple weeks to the bottom. Once there they stay there until you stop the system.

If you don't want to gradually lower the diffusers then you should use the slow start described by Burger above.