My fish continuously nibble on plants!?

All of the mollies i have ever had have done this. It is normal. They eat algae off of the plants, rocks, ornaments, slow moving fish, you name it. They are about as busy as danios are. If you want to inject a bit of concentrated algae in their diets you can try algae wafers or algae flakes. Both contain spirulina which is beneficial for all fish.