I agree having a clean tank makes for a happy birth, and a better one. If the water is bad/unclean the babies will mostly get sick or be deformed. I knew my molly was going to give birth because she gave birth last month on the late evening of the 24th or the VERY early morning of 25 because I woke up to fry. She must like to drop them in the night hours. When you see fry from this molly, look to that date of the next month. Example, my molly gave me fry on 4/25/12 and I knew to look for more on 5/25/12, 6/25/12, etc till she is out of babies. I have no males so hopefully she'll be done having them. if you have males, you'll be seeing a lot more. She gave birth to only a few fry, I increased my plants in my main tank. I saved three. Even though I fed VERY well the previous night, had lots of plants for hiding and no light on. What can I say Tetras like Molly fry.