<<One, just to be certain, putting two four week old males with three seven week old males should be okay, right? I have heard a few times on the list that people have had this work, I jst want to be certain before next week.>> Just to be safe, I would recommend using the split-tank method to introduce them. This is how I introduce all of my gerbils, and I think it is the best, and safest, way to do it. Yes, your gerbils are all still young, but do you want to chance a 7 gerbil rumble?? Best of luck! ~Lanie AGS member and registered breeder *Royal Star Gerbils* http://www.angelfire.com/ks2/royalstargerbils
