can anyone tell me what my fish died of?

A couple of weeks ago I bought a male Comet Swordtail which promtly died after 48 hours (he looked fine in the shop). Then 24 hours later my betta died. The back half of his body seemed to become rapidly covered in a greyish white colour which disolved his fins. I was told by the shop to use melafix to treat the tank which I did but now one of my swordtail fry has just died from the same thing. This time it appeared to start with a patch of scale that lost colour on his head and then oprogressed to disolve his fins. The shop told me that fungal ionfections aren't contagious so what is going on?

I change the water every 2 weeks. I tested the water and my reading are:

nitrate 10
nitrite 0
ammonia 0.25

 

Hi Boo Boo Magoo, As usual the shop is about half way there. Fungus is not transferred from one fish to another. It is however a result of conditions in the water, so that in a sense it is transferred from the water to the fish. What new decorations have you added to the tank recently which could have some imbedded organic matter. Also, are all of your fish accounted for or is one missing that you have not been able to find. A dead fish decaying in the water will very rapidly degrade the water conditions causing fungus.

 

Hi, all my fish are accounted for, I have however recently added some new plants and a resin ornament which I pre soaked. I have retreated the tank with some of waterlife's protozin and everyone appears well for now.

 

It's not likely anything to do with the resin ornament, but be careful using decorations that aren't designed for aquarium use. Sometimes the paint or sealant on them can be toxic for the fish. The most likely cause for the fungus at this time is the live plants. Any decaying organic matter can cause fungus. Be sure to pinch back any dead growth, and remove any bulbs or root system where the plant has completely died. Usually, but not always, when the plant decays you can see the fungus begin to grow on the dead residue.