Try to set up the 40 as close to exactly the same water parameters as the tank they are in now. This will reduce the stress of the move as much as possible. Also, make sure you use some kind of agent (i.e. prime, Stress-zyme, Novaqua, etc) to help age the water before you put the fry in. All this helps reduce moving stress on the fry. Once the fish have adjusted to their new surroundings (i.e they are eating), then you can start to gradually change things. (In my case, most of the places I will be selling my fish to have a harder & higher PH water than what I will raise mine in. That means that as they grow, I will be slowly adjusting their water to be more like my Tap water instead of the soft , low PH water they were hatched in. Change is fine as long as it's gradual. Thank goodness Angelfish adapt pretty easily to change, just not to rapid changes. Good luck with the move