I have purchased that vial of liquid that "fell off a truck" but have no idea what it's supposed to do as it seems like it does nothing. Any help?

It works best when you use it in a tank that's full (or nearly full) of adult fish. It does very interesting things and can help advance your breeding program, but it doesn't affect every fish in the tank.

Thanks LadyCFII, I'll try it with a full tank. Do the adults have to be pregnant?

It doesn't matter if the fish are pregnant or not, since that chemical affects only the fish in the tank and not the unborn offspring.

will it affect the magic fish or should they be taken out of the tank first so that they are not lost? and should I keep one of each magic fish in each tank?

It has the potential to affect any fish in the tank that it's used in. I never leave my Magic Fish in a tank where I use that chemical. Whether or not to keep any or all Magic Fish in each tank is entirely up to you, and depends upon the effects that you're looking for in each tank.

thanks

does it always do something different?

Its effects are random and depend upon what fish you have in your tank. As I said earlier, it's best to have a tank full of adult fish before you use it.