Sivabiot, a green water bloom is just the opposite. It is beneficial to the fish. The only negative about it is that it makes the fish a bit hard to see. Standard advice for a commercial breeder in a place that is warm enough for outdoor ponds is to fertilize the water a couple of weeks before adding any fish and wait until the water is regular pea soup before adding the breeders. If green water was a problem, that would be some terrible advice for the agriculture department to give their fish breeders but is exactly what I find when I go to the AG website.
In addition, a commercial breeder of endlers, that I sometimes write back and forth to, has said that when he has fish that just don't look up to par, he throws them into a green water tub for a few weeks and the improvement is amazing.