Update on: Ogon goldfish project

In June 2015 I wrote about the prospect of doing a unique project, that is to create ogon goldfish. To refresh the memory, please read the following post:

Ogon goldfish – is it possible?

Now, it has been 10 years since I wrote about it. Nothing has been done so far. Until at the beginning of this year (2025) I met a koi breeder and judge, mr Kevin from Surabaya. He specializes in breeding ogon koi. And he is kind enough to give me two baby male ogon koi from his breed.

I kept the ogon koi in a small tub, in the hope that they will not grow too large. I want to make a cross between the ogon koi and goldfish. The purpose is still the same, to create goldfish with shiny metallic fins and tail like the ogon koi. Well, if it can be achieved, I believe it will be a new unique and beautiful specimen of goldfish. Last time I try to make an illustration of such fish using photoshop, which might not be eye-catching due to my limited skill. Now, I ask chatgpt to generate the fish I envision. And see the difference between my normal tosakin and the envisioned ogon tosakin below!

The two ogon oranda below are also generated by chatgpt:

Marvelous, aren’t they?

So, instead of employing the purely selective breeding strategy, I will use the crossbreeding strategy between koi and goldfish. The ultimate question is: is it possible to cross between two different species?

Well, I am not uninformed about this. Since high school I was taught that such cross is possible but the offspring will be infertile. The case being mentioned was the cross between horse and donkey. I believed that theory until lately.

It happens that I enjoy following the scientific new discovery on prehistoric human. We now know that we as homo sapiens were not alone hundred of years ago. There were homo neanderthals, homo denisovans, and some more. They were considered extinct right now. But the DNA research shows that they leave a trace in our DNA. This information shows that it is possible to create fertile offsprings from species crossing. One of the podcast (I forget which one) raised up a question of how this is possible. The speaker explained that species categorization and the conclusional theory about infertility in the species crossing are man-made, and nature does not follow human’s categorization nor theory. Well, it was an enlightening explanation for me.

Then I went back to the case of crossing between horse and donkey. I ask chatgpt to find information about such crossing and whether there was a case that does not conform to the theory of infertility. And guess what? There were several documented experiment on such case! the record showed slight chance that the female F1 of such crossing were fertile. When they mate with male donkey, the offspring (F2) are donkeys. The AI does not find the case of crossing back to horse. And no account of fertile male F1. Well, I do not dig deeper. I think this information is enough for me to conclude that koi and goldfish can mate, and there is very slight chance that the offspring are fertile and I can cross them back to goldfish, provided the specimen carries the metallic fins genetics as in ogon color. Yes, I know it highly depends on luck. So, I need lots of best wishes from all the hobbyist who read this diary.

In the goldfish world, I have with me a paper from 2008 titled “The formation of a diploid gynogenetic hybrid clonal line of red crucian carp x common carp, and its application” by Shaojun Liu, Jing Wang, Wei Duan, Min Tao, Jifang Liu, Chun Zhang, Kaikun Luo & Yun Liu. It seems that they were doing the same experiment with koi and goldfish. unfortunately, the paper is too technical for me to read. I do not have enough background to understand what it says.

So, back to my project. I am glad to report that I have done the first attempt of crossing. My two ogon koi has come to maturation, and I mated them with a tricolor oranda. Why such pair? Frankly, no reason at all. Everytime I put a productive female goldfish in the tub with the koi, the goldfish stop laying eggs. The koi has never chased the goldfish. This was frustrating. So, when a goldfish was laying eggs in another pond, I strip the eggs and strip the sperms of the koi on top of the eggs. Yes, hand spawning. It happens that the tricolor oranda was laying eggs in another pond close to the koi tub in my facility, so I just grabbed the oranda and mate her with the kois.

These are the pair:

From the forced mating, only three eggs hatched! So few! But the successful hatching gets me excited! The ofspring is already two months or so, I think. And here they are:

At this stage, the metallic in the fins and tails is below my expectation. But the metallic color in the head (mouth and gill) is a trait I was not expecting, though that trait comes in varied degree in the. I cannot see clearly if they have moustache like the koi or not at this time. Well, I guess I can only wait for them to grow up and observe their progress for now.

I mated the koi with the tosakin with the same strategy twice. Nothing hatched at all! I do not know why. I also mated the koi with orange oranda (a cross between purple oranda and black oranda) and got a lot of healthy fry – more than a hundred of them. They are 2 cm in size right now. I will update on them later.

That’s all my report for now. If you are excited about this project, wish me the best!