my teacher has a fish tank with guppies and a pleco. she just got the pleco and all her fish are dying. when they die their fins are partly, i dont know, just gone. i think it is fin rot from the new pleco, becuase the pleco has fin yucky stuff on its fins. is their anything i can do? any treatmentor medicene? or just let the guppies die, becuase she said the same thing kinda happend last time a while after the guppies had babies. its been about 5-8 months since they had the babies. i dont know, just if any one has any help, my teacher will appreciate it. thankyou.