When to Transfer a Goldfish to a Pond
How large must a goldfish be before you can transfer it to a pond?
Size is probably the last thing that needs to be considered before transferring a Goldfish to a pond.
A newly hatched fry a few millimeters long can be put into a pond as long as there is available food and no predators present, which includes other Goldfish.
My checklist would go something like this:
1. Is there anything in the pond that will eat my fish? This includes larger Goldfish or any other wildlife that would consider a pond a natural home and food source.
I am assuming your fish has a body length of 25mm (1 inch) or larger. This eliminates most predator "bugs" that can kill small Goldfish.
If there are Goldfish already in the pond, your fish should be at least a third the size of the existing fish otherwise although Goldfish are considered non-aggressive, any new fish in their environment are considered food until they get used to them.
2. Water conditions. Goldfish shouldn't be put into a pond during winter because they haven't had time to build up a fat reserve. Even early spring is usually too cold.
I put fish out into ponds in late spring through to early autumn when temperatures are above 15C (60F).
The water should be tested to ensure the pH is around 7.00, ammonia is zero and nitrates are below 50 ppm.
3. Goldfish varieties all have different care requirements.
Don't mix fancy varieties with single tailed varieties, as the single tailed fish will always get to the food first.
4. Unless you are absolutely sure that cats and fish eating birds can't reach the pond, it should be covered.