okay, we have a 55 gallon tank, with a cartridge filter, and all that stuff, and we did a water change about 5 days ago.
There is one guppy that weve had since the original tank, and although she has been perfectly fine (pregnant but fine), now she has a huge gaping sore on her side (see photo). We dont know if she was attacked or if shes sick (people at the petstore seem to think shes sick)
my mom put in maracyn-two by mardel this morning to see if it would help- we just separated her from the rest of the fish... HELP!!!