illness

I have a community fish tank that has been fine for awhile, I recently bought some new fish from the pet shop, which I think introduced something into my tank. All of my guppies are dying, they are the only type of fish to be affected, the bettas, tetras, loaches and catfish etc are unaffected...

I have been trying to treat my Betta for a large swollen side and very little pooping (though he is still active and eats like a horse). The spot is very large focused to one side as well as transparent (with only a tint of yellow). This issue has been going on since a bit before New Years and...

can anyone advise me. my fighter has, in the last two days, had a strange looking white patch on his scales next to his tail fin(not on the fin) also his dorsal is half missing. is it fin rot? does fin rot affect scales? please help!!  i would upload photos but i cant seem to get the files small...

In the past month, I've lost a Mickey Mouse Platy, a Swordtail, and I'm on the verge of losing another platy, and they've all displayed the same symptoms, but only one fish has been sick at a time. The symptoms are rapid breathing and fin movement (they look like they're struggling just to stay...