If you have a domestic water source that does 7 gpm you can rig a three-way from your outlet and run three hoses to the pond. Each hose can be attached to a sweeper nozzle which delivers 2.3 gpm at super high pressure. Each hose can then be placed toward the center of the pond, below the surface, in three different areas. If oriented upwards, from about eight inches below the surface, each sweeper nozzle will create significant surface agitation without disrupting any small thermocline you may have. This will have the dual effect of delivering slightly cooler water, breaking up surface tension to increase overall DO and giving your trout another option.
Remember, trout will chase adequate DO before they'll go to adequate temps. If your trout are lingering in the warmer water, then you most certainly are having a DO crash.
