(Port Perry, Ontario)
I have a 135x65 feet pond 20 feet deep in the center. I released 30ish goldfish with 2 of them being 8 inches long and full of babies...
So now we are almost into October and I have thousands of small black fish from 3/4 inch to 3 inches long, what can I feed them?
Being in Canada the pond is going to freeze, will I lose all of them (I have an aerator which keeps an opening in the pond).
What can I expect as far as numbers 10,000 1,000,000
You do things big in Canada don't you!
At an average of 10 foot deep that calculates to 656,000 US gallons.
Obviously the conditions you have provided are ideal as you wouldn't get that many goldfish fry otherwise.
If the fry are black, they are changing color. The color change starts around 50-60 days old (depending on temperature) by the fish turning black, then gradually lightening up from the bottom. They will turn yellow orange, some white or a mixture of both. The colors will deepen over time.
At 3 inches in body length, these are now juvenile fish. They can eat what you are feeding the parents. The smaller ones will find it tough going as the growing season is coming to an end.
Goldfish do survive freezing as long as there is an opening in the ice. Your aerator will do this nicely. The smaller individuals under two inches in body length probably won't have enough body fat to last through winter. Keep feeding them until they show little or no interest in feeding and then stop until the ice starts to thaw.
As far as numbers you can expect, many factors govern this figure.
The pond surface area is 8775 square feet. This will safely support 26,000 1 inch goldfish.
If the pond isn't covered, predation will be high from birds, especially once the fry turn gold.
High summer temperatures can cause large die offs. The aerator (which must be a big one), will help, but toxin buildups from green algae can cause pH spikes.
If left to breed naturally, as the fish numbers increase, cannibalization rates will also increase, so for example next year's spawns won't produce the same number of fry as this year unless you intervene and remove a large number of the juveniles.
Fry that don't change color and remain the natural silver gray color will increase in numbers over time as their survival rates will be higher than their colored siblings. They will degrade your fish population over time if they are allowed to breed with the colored individuals.