Counting fish can be very difficult in a crowded tank! One way to make that task easier in the Windows version (if you're running in windowed mode) is to 'click and hold' on the title bar of the window. The fish will stop swimming while you're holding the mouse button down, and you can count them much more easily (except, of course, for the fish hiding behind objects in the tank).

Fish will produce one fry with each pregnancy under 'normal' circumstances. The Magic Fish you refer to will increase that number by one, as will one of the plants that's available for purchase in the Supply Shop. So, depending upon what 'extras' you have in your tank, each fish could produce up to 3 offspring, but it's always predictable.