There is one thing that might have happened to cause the problem you saw. If you go to the menu and change players, and then change the game speed setting before you click Play, the game will update the tanks based on the new speed setting, and not the speed setting you had previously. You need to always click Play when you change players to make sure that nothing bad happens, and then you can change the game speed setting.
Oh, thanks! I didn't like Fish Tycoon at all 'cause all my fish would always die! I just decided to play Plant Tycoon instead.