my fish keep dying!

Question
hi there
i have a 29 gallon tank that has been running for about 2 years with no problems. i do the regular water changes, gravel vacs, filter cleaning. the last 2 months i have just about 2 fish die every couple days.  have had the water tested for everything they test water for and it all comes back normal. all i have is a pleco and guppies. every time i see a dead one the fins and tail are gone. i have called the petstore that i buy them from and they at first told me it sounded like rot tail or something like that, so they gave me the stuff you put into the tank to help with that.  it seemed to clear up really nice and for about 2 1/2 weeks had no problems at all and the fish had stopped dying.  BUT now they are dying again.  im not sure if maybe there isnt enough female guppies or something but i dont know how to tell if they are female or male anyways.  last week i bought a bunch of females to hopefully make the males happy but they still keep dying. what could be causing them to die what am i doing wrong? i miss my tank being full! my kids miss my tank being full! fish are costly to keep buying so they can turn around and die ...please help
jenny

Answer
First I would question the store you are getting them from. The fish must not be bred well and are weak fragile fish and that seems to be why they are dying. The way to tell a femal guppy from a male is the tail and color. The males have big tails which are super colorful while the females are more subdued in color and have smaller tails. The females are also usually bigger than the males. Based on what you have told me, my quess would also be fin rot but to have it happen on a regular basis is puzzling. I would definately find a different fish store. The one you are going to does not sound like a good one. Guppies are super hardy fish and should not be so easy to die of a disease or parasite. I would treat the tank with the treatment again and follow the directions. After treatment I would clean and change 25-35% of the water, this helps remove the treatment. Make sure to not use your carbon while treating and be sure to replace it after treatment. Use a brand new carbon filter when you are finished treating. Do that and than slowly add one or two fishes. Dont add a lot at once, this may also cause stress. Also, be sure to acclimate the fish to your water correctly and NEVER put any fish stores water into your tank. I highly advise finding a new store to get the fish from. I hope I have helped you. It simply sounds like a fish store that doesnt care has been giving you the guppies and they were sick to begin with. Let me know if you need more help on anything. I know how expensive it can get but the result is beautiful when it works out. Hang in there and take it slow. Let me know how it goes.
                                          Rachel A.