fishies dying

Question
I have a 20 gallon tank with about 15 male guppies and 8 female guppies and 3 corries in the tank.  A week ago i purchased 8 more guppies and 2 coolie loaches.  It was a 5 hour drive for the new fish so we knew they may have a hard time. I removed the females and added 4 male guppies from another tank.  4 of the new guppies I purchased and 1 loach did die (with no surprise) in the first 2 days the fish were put in the tank.  However it has been a week now and several of my original guppies have died and just yesterday 2 of my corries have died.  The dont look sick, they just seem to be dying over night.  Also the females I removed and doing fine.  I dont know how to check the water in the tank but then I've never had this problem beffore.  My orignal guppies and corries have been around for a year or more.  Any suggestions as to what may be happening?  Thanks in advance.  

Answer
hey Ken,
your tank might be a little bit overcrowded, which can cause stress and sometimes death (form being to stressed and going itno shock, etc.)
it could also be becuase you have so many male guppies together. males tend to be slightly aggressive, dominant, and competitive for females, so when they are with a bunch of other males and no or little females they beat the crap out of each other. This is very stresfull for weaker and younger males, so having males with an equal or greater number of females should help.
like you said, the newer ones that died was probably from the stress of the 5 hour car ride and being in a bag with little oxygen, and the stress of a new tank and habitat and tank mates, and it is possible that the fish were sick when you bought them.
Since they dont seem sick at all, i think it is just stress. If you can try to reduce the crowding in your tank and get a higher balance of males and females, then you will probably have better luck with them.
The older fish probably died just becuase you added so many fish at once.

It might not necessarily be crowded, but it could just be becuase you added so many at one time. That may have just stressed all of the fish out.
If you're worried about keeping males and females together becuase they will breed, then try calling up a local pet store that sells fish and see if they would consider hireing you as a breeder. Even if they dont pay you and just give you store credit, its still fun to breed and wont have your tank overcrowd.

good luck with all of those guppies and corys!
best wishes, chelsey