Hi Rud! Welcome to AA!
It really depends on how strong that certain fish is! I switched tanks and slowly administered all my fish (which were only about 8 into a 50 gal
.) so that nothing would spike, and one of my mollies died, but the other mollies were fine, so were the danios and guppies! All of those fish are very hardy...I'm not sure about the gourami, I haven't had much experience with gouramis...Also, cycling a tank is anywhere from 6-8 weeks OR it can take even 3 months! It depends on your water.
Hope I helped!!!