Hi George, issues I have seen with surface aeration in our northern ponds in the winter are when the power goes down and the ice moves in they can get destroyed quickly.Often running them all winter is not needed or wanted for our warm water types when temps are teens down to zero. (The larger the pond the safer they are for winter use.)Then surface aerators are difficult to remove with thin ice.I think for warmer climates and high biomass situations they are a great tool.I have not experienced a winterkill with properly placed equipment and a good understanding by the pondowner when and when not to run bottom aeration.Perhaps with our colder water holding more DO and lower stocking rates winterkill is not that much of an issue.You mention if conditions worsen you might kick in the bottom diffused and that may make things worse.Consider mixing that water before things get worse,with the surface aeration. If they are in less than 8 ft of water at normal pool ( is full pool rare)look at your disc spacing and see if Todd can repipe the discs as close to each other on the base as possible for more lift.If less than 8 ft have the discs touching each other will give more lift than if there is a spacing between the individual disks on the weight base.Hope you get that 3 ft back soon, take care !!