I have a 75gal tank that has 40 adult fish (2 mollys, 12 platys, rest guppys). I have had a habit of when buying fish I look for the pregnant female and it has left me with a tank full of babies (ex. got a preg black molly and the next day I had 13 black molly babies). I know that getting pregnant females from the store usually causes them to give birth in the first couple of days from the stress of going from tank to tank and have played on this "normal" event. The last time I attempted to catch them all and move to a breeder net was when i drained and moved my 75gal just a couple of days ago. I lost count once I hit 50, although I think there is less than 60. I had 7 pregnant female guppys that dropped their babies in 1-2 days. I have two pregnant platys and 3 guppys still to give birth. They have plenty of stuff to hide from to include my gravel. My gravel is like small pebbles and they can snake their way all the way to the bottom if they want to.

My question is how long do these fish take to completely mature? I know I can google that, but thought you all would know.

Not worried about overstocking. Most, if not all of my platys and mollys will be moved to my 125gal as soon as it has cycled. At this point I intend to buy only a few fish from here on out. I want some more mollys and may get some silver and dalmation. I also want some red wag platys. After that I think my tank stocking will take care of itself.