Actually this is the result of having the pipelines into the pond shut off for 8 weeks and it all getting flushed into the pond once the circulation system was turned on.
This was all anticipated and planned for. The “scum” will be swept up now and the new recirculation system should keep it clean once all the gunk from the pipes is removed.
This is not residual algae. This is not sabotage. This is not sea monkeys. This is not going away. This is the result of incompetence and creating a heat sink in a shallow non chlorinated pool.