I have been our of the tropical fish game for 10 years, I have just set
up a new tank that had goldfish in, replaced all the internals except
the pump head etc.
I left the tank for a week and then addedd some fish.
Then the problems started, the waste food on the bottom looks as if it
has fungus growing on it, I can email pics if this helps, I have lost
all the fish and I am lost for advice.
I have tested the water and the results are as follows:
Ph 7.8
Ammonia 2
Nitrite 0.5
Nitrate 0

Any advice on what it could be and what could be used to treat this
before adding and more fish would be greatfully appriciated.

Regards

Mark