I'd say if you're going to upgrade in due time go ahead and get them but I kept them years ago and they do get big. Just don't keep them in that tank for any extended period of time and really try to get a group. 2 Fronts are not a group! I'm not an expert but i would say get at least 5 to 7. Good luck.
Larger amounts of fish dont need to be culled unless you have a huge sausage fest......and if you where to cull the colony down, only do it to wild caught ones.....F1, F2's and so on.....you should cull all the males and get another male from a different colony....try to bring in new blood lines......