I've never experienced a DO issue behind SONAR treatments. Not saying it can't happen. But, the product works VERY slowly - unlike many others. Still, if the conditions are ripe for a DO problem, it can certainly happen.
The pellets might be easier, randomly dispersed. Not overly critical that you achieve even coverage - but you must apply enough product relative to the total volume of water in the pond.
Have you had the water's salinity tested? Reason for asking: I've only encountered this specie (in TX) within brackish (inland) river-impoundment lakes - ie. Lake Granbury & Possum Kingdom Reservoir, as examples, both of which are fed by the Brazos River and are relatively brackish.
