what's causing my goldfish to die?

Water levels are perfect (ammonina, nitrate, ph good), but I've lost two
goldfish in the last week. I have a 55 gallon tank with sand bottom, do
bi-weekly water changes of 25%, running a Penguin bio-wheel filter, air
curtains.

The last fish (Lionhead) developed a nasty case of fin shredding and laid at
the bottom of the tank.
The other one (Oranda) laid at the bottom of the tank without any visible
signs of problems.

I've noticed on one of the remaining fish there was a bit of white fuzz on
the mouth, but that has disappeared.

The other couple of fish seem perfectly happy (no signs of problems).

Any ideas?

Rodney,

You make no reference to NitrItes? The white fuzz on one of your fish
could very likely be columaris or some other fungus.

Also is the temperature fluctuating at all? How many fish do you have
in your 55 gallon?



Rodney wrote:
>
> Water levels are perfect (ammonina, nitrate, ph good), but I've lost two
> goldfish in the last week. I have a 55 gallon tank with sand bottom, do
> bi-weekly water changes of 25%, running a Penguin bio-wheel filter, air
> curtains.
>
> The last fish (Lionhead) developed a nasty case of fin shredding and laid at
> the bottom of the tank.
> The other one (Oranda) laid at the bottom of the tank without any visible
> signs of problems.
>
> I've noticed on one of the remaining fish there was a bit of white fuzz on
> the mouth, but that has disappeared.
>
> The other couple of fish seem perfectly happy (no signs of problems).
>
> Any ideas?