Back to Back Issues Page

The Goldfish Gazette, Issue #009 -- How to Cull Goldfish Fry
September 30, 2014

Goldfish Care Tips and Guidelines

A Free Monthly Resource For Goldfish Enthusiasts
September 2014
Issue #009

In this issue
How To Cull Goldfish Fry
What's new on the Website

After you have successfully bred your goldfish, you probably have between several hundred to several thousand fry.
Unless you are a commercial breeder, you need to quickly reduce the fry down to more manageable numbers.

How To Cull Goldfish Fry

Following on from last month's E-zine about Goldfish Standards, we will describe how to cull goldfish fry so only the best are grown to adulthood.

From the number of visits to the website pages on raising and feeding fry I can safely assume there were plenty of successful spawnings.

A successful spawning will produce between several hundred to perhaps several thousand fry. Unless you have unlimited space you can’t possibly raise them all.

If you don’t cull them, nature will decide which fry survive.

For single tailed varieties this isn’t such a problem because the characteristics you are looking for such as color or finnage develop relatively early at about 2 months.

The only culling you can do until then is for physical deformities such as missing fins or eyes, bent spines and separating out larger individuals to stop cannibalism.
You also need to work out how many fry you can grow in the space available that allows them to develop properly and cut numbers back to suit.

Fancy Varieties Require Much More Work

Fancy varieties are an entirely different matter. If you let nature take its course, all you would be left with are fry with so many faults they wouldn’t be worth the food you fed them.

Even after centuries of selective breeding, fancy Goldfish varieties don’t breed very true to type.
A large number of fry in any spawning will have faults caused by their dominant genes wanting to revert back to the original wild goldfish the Prussian carp.

This means if you don't cull out the rejects, those fry that most closely resemble the Prussian carp will have the best chance for survival.
Here are some examples:

Fancy Goldfish varieties should always have two caudal or tail fins. If several hundred fry from a large fancy variety spawning have one caudal fin, who gets to the food first or is quickest avoiding enemies? It is the single caudal fin specimens.

Celestials should have upturned eyes and no dorsal fin. Those Celestial fry with a single caudal, a dorsal fin and normal eyes are going to dominate the higher quality fry.

You get the idea, the more developed the variety is, the less likely the high quality specimens will survive.

You can argue that if fry are kept in an aquarium, and fed all they can eat, you eliminate the problem of enemies and competition for food.

This is correct, but unless you have unlimited space, fry that are cramped are more prone to disease and stunted growth.

But who wants to spend time and money growing fish that have no value as breeders and little if any value to other goldfish enthusiasts?

Start Culling Early

Fancy Goldfish varieties show some of their traits early, twin caudal fins being the first.

If your fry are growing well, at two weeks of age you should be able to cull for caudal fins. You won’t be able to see too much detail, but single tailed fry are obvious. Any with a webbed tail (top lobes fully joined so there are only three lobes) should also be removed if you can see them.

At four weeks cull for caudal fins again. You should be able to see webbed caudal fins clearly and whether the top lobes are partially or fully divided.

Dorsal-less varieties should be put in an aquarium as soon as dorsals appear and be viewed from the side. This can easily reduce the numbers of fry you thought were good by half.

You should be culling fancy varieties every two to three weeks. Each cull should halve the number of fry.

From about 8 weeks telescopic eyes start to develop and finish in another 8, so this provides another opportunity to cull.
By this age you should have finished basic culling for finnage and physical deformities.

As the fry grow larger they will show more faults, so culling doesn’t stop until the fry are adults.
Culling fry regularly is the secret to raising high quality goldfish because it gives the best specimens every opportunity to develop into champions.

What's New On The Website

Ranchu Goldfish

I have added a page on Ranchu goldfish because I had fallen into the same trap that a lot of goldfish publications do, lumping Lionheads and Ranchus together as if they are one and the same variety.

The majority of care and breeding requirements are the same for both varieties, but each deserves their own page.
If an enthusiast wants to breed either variety, they need to be aware of the differences that separate them.