Take as much water as you can from the main tank and put it into the 22L tank then transfer the babys over somehow (by themselves) and put a heater in with them(set to the same as the main tank!) They wont need heaps of water to start off with, just enough to keep them there, plus put an airstone in if you can. Just put another cup full into the smaller tank every few hours until it is at a level you are happy with. That way the fry wont get shocked too much by water parameters... Other than that theres not alot else you can do. if these ones dotn survive, setup the small tank and put the pair in there to breed, and when they do, take them out and chuck them back into the other tank (or leave one or both there if you want)
HTH