Something is wrong, because you should have no trouble with common eggs/common fish even at the very beginning of the game when you have Level 1 of Fish Environment. What, exactly, happens when you hatch common eggs? What species of fish are produced? Have you ever used the Unknown Chemical? When you first started the game, did the fish from the starter eggs die, or were they OK? Sorry for all the questions, but I'll need more information in order to figure out what's happening in your game.