How Old Are My Goldfish Fry?
I have just noticed some small goldfish fry in our outdoor pond.
They are about 1.5cm long. How old would they be? And how big do they need to be before they are safe from being eaten by the adults? Thanks. Marie
Assuming the parents are slim bodied fish, a Goldfish fry can attain that length in 4-5 weeks from the eggs being laid.
They may be much older than this because several factors dictate how fast fry grow. These are:
1. Water conditions. Because the adults spawned, we can presume water conditions are good.
2. Space. At 1.5 cm space isn't too much of an issue yet unless there is a considerable number of fry, but I suspect the adults have cut down the numbers substantially.
3. Water temperature. Being late summer/early autumn when the eggs were laid, the water temperatures should be in the high teens/early 20s C, ideal for fry.
4. Food. This is the big question. Depending on the number of fry, the amount of food available will have had the most impact on growth rate. Initially the fry will have eaten small protozoa and anything else they could find that the adults wouldn't bother with.
At 1.5 cm they would be eating whatever you are feeding the adults.
Having observed fry in one of my ponds, and the slow growth rate because I wasn't feeding them, my guess on age would be from 6-8weeks old, but they could be older.
Your second question regarding the size they need to be before they are safe from the adults, they would need to be at least one third the size of the adults.
Anything that can fit into their mouths is fair game for the adults. Fry any smaller than a third can be chased and their fins chewed by the adults.
With the temperatures starting to drop now, if you want to keep any of the fry, I would suggest by the end of April they will need to be brought inside for the winter as they will be a little small to be outside.