Personally I don't like dissing anyone in public but take it from me the above reply is from Muhammad Saleh Al-Munajjid who has been refuted by many scholars for many many reasons. Yes some people still quote out of him and still regard his opinions but to them I must just warn that as the final hour gets closer true knowledge will be lifted and calling to falsehood will increase..Audubillah from such trials!
Scholars advice brothers to always tell your wives as its of good manners and good character to do so. and they warn them to do unto other women what they would want for their own daughters,mothers,and sisters. Its understood most women will feel jealousy at some point but the choice is the first wife's too. You can stay married to him and accept your co wife or divorce him. This is a choice you have.
I know for many non Muslims and even many Muslims they may see it that in polygyny women are losers but trust me when I tell you, as I have now many friends from all over the world who are co wives, the blessings in polygyny are there too and maybe sometimes more for the women than the man! But that said let me add none of my friends husbands married them through flirtatious liaisons rather they all married the manner which I mentioned before, Alhamdullillah! And maybe thats why these women will tell you only the blessings of having co wives, Allahu alim!