I'm surprised there would be no trace of nitrate. Nitrate is the end result of the biological cycling process. It's normal to have SOME nitrate. I try to keep goldfish tanks indoors at ten parts or below. How recent was your water change before you tested for the nitrates? How long has the pond been filled with water? What's the gallons? How many fish?
During the establishment of a biological cycle (usually taking 30 days), nitrites will be present. Once the "good guy" bacteria build (mainly in your filter component), the nitrites will be eaten as part of the cycle. In a new enclosure, it is normal to see nitrites present while the tank cycles.
The color black is the least stable in goldfish - which is why so many people who buy black/gold fish complain later on that their fish turned completely gold! Black can also be a sign of trauma - like a bruise and also ammonia burn.
I was a moderator on a fish forum for some time - my specialty was their cold fish section (goldfish).
Do you have photos of your pond? I always enjoy seeing them!
During the establishment of a biological cycle (usually taking 30 days), nitrites will be present. Once the "good guy" bacteria build (mainly in your filter component), the nitrites will be eaten as part of the cycle. In a new enclosure, it is normal to see nitrites present while the tank cycles.
The color black is the least stable in goldfish - which is why so many people who buy black/gold fish complain later on that their fish turned completely gold! Black can also be a sign of trauma - like a bruise and also ammonia burn.
I was a moderator on a fish forum for some time - my specialty was their cold fish section (goldfish).
Do you have photos of your pond? I always enjoy seeing them!