I feel like I am missing something here. Looking at the pics I thought the bloom was strong but that there was sufficient clarity so as to be a low risk for the fish. I had missed the part where the OP had previously applied alum but it was not clear whether this was in response to suspended clays or too much bloom. If the former, sunlight itself may have been limiting to forming a bloom or a combination of this and the co-treatment of lime with alum. I guess my sense was that the bloom would stimulate a bloom of phytoplankton grazers ultimately lowering the standing weight of phytoplankton while feeding the fish and insects in the pond.
It's a young pond entering its second year and the OP didn't think it carried a large load of nutrients so for those who expressed a great deal of concern and suggested corrective action, I am interested in understanding why you felt alarmed and in particular the evidence you are relying on to make the determination.
