You need to research any chemical before deciding whether/how to use it.Algaefix has has three main issues that can endanger fish. It can have direct toxic effects, it can reduce oxygen in the water, and a large algae die off can cause ammonia to build up in the water.With this in mind I used it at about 1/3rd of the recommended dose, just once. This is in contrast to the dose given on-label of three full doses.It knocked back the algae with no noticeable effect on goldfish, snails or plants.
Rating: [3 of 5 Stars!]