Help, lost one of my panda Corys and don't know why?

[Marne]

Just found one of my panda Corys dead, no marks on him, no signs of disease. Checked water and all seems fine, nitrite 0, ammonia 0 and nitrate 5. Tomorrows water change day so will give the plants a bit of a clean ( as they look a bit dirty ). Havn't lost any fish for a while so seems a bit odd. Any ideas?

Is this in your new tank? Did you quarantine all the newcomers? Have you been adding stock gradually?

Yes, havn't added anything for a month, pandas have been in there a while, no sign of illness in any of the fish, a few of the guppies are near the top of the tank though, water has been perfect for ages, was going to get a male swordtail soon but will have to wait now. Will do a water change to or row, hopefully that will help.

Not sure if my filter is turned up enough, I don't really understand externals, the setting ( leaver thing ) is in the middle, I turned it down from full blast a few weeks ago as I was worried it would suck up my swordtail fry, other than that nothing has changed.

I don't think it's the filter. You seem to lose a lot of fish, I wonder if there's a bacterial infection that's hanging around? Or maybe your water test kit is faulty?

Eau, I havn't lost hardly any since getting the new tank ( just a couple guppies in the first week ), I have still got all my guppy fry from my old tank, lost one gourami but that was sick when I bought it ( died 2 days later ), all the others seem fine, if it was a bacterial infection surely my other Corys would be poorly and other fish?