Fish with white patches on his side. Patches start small but grown slowly, over months. Finally, they appear like a mass, then ulcerate. The fish does not appear sick now, but will be sick by the time the mass appears. They die after it ulcerates. It is contagious, since several fish in the aquarium have died from this malady. Most of them were swordtails.
55 gallon, well established tank, pH 7.2, temperature 80 °F (27 °C), no nitrates, nitrites or ammonia. Two 55 watt compact fluorescent plant growth lights. Filtration is external Marineland filter. 20% water changes once or twice a month.
In picture 3, 1 and 2 are not accurate. The first image shows what they look like best. They pretty much all look the same (they're small and match the scale pattern well). All of the fish have one at their anus and have them at their lateral line; however, only pearl has one under her top fin. Pearl's appear on both sides; however, red's only appear on one side. I'd love to see my fish stop dying. What is this?