How many fish were in the tank at the time? Were they adults or immature fish? As I mentioned in my answer to your other question about that chemical, you really need to have a tank full of fish in order to increase the chances of having an effect. It usually affects only a small percentage of the fish in the tank, and it's easier to see any effects if the fish are adults.

If you had only immature fish in the tank, you may have to wait until they are grown to see if anything happened. If you had only one or two fish in the tank, you may have, as you said, wasted $650.