Yes get it to put your mollie fry in it. If he has the bottom filter system to it that is good. Take water from the tank the fry are in. Set up heater in it over not so the temp will level out .Goto walmart and get the heater for a2-5 gallon tank. This will keep water temp good. Put fry in plastic bag like you get them from the pet shop. Introduce them like they were new fish going into a new tank. Let the water in the bag they are in get the same temp as the tank. Then put them in it.
I raise mollies, guppies, platies, swords all together. Mollies and guppies go good together. I keep my tank water between 76-78. In the past week i have had over 300 fry born from my guppies and my mollies. They like it. Remember the rule of thumb. 1 male to 2 females. This will keep the males from picking on just one female.
Good luck
Goto my web site and see pic of my tanks and info on how to take care of frys located under my blog