Sexing clown loaches

[RD.]

The only way to be 100% certain about sex, is when a female becomes gravid. There is no other definitive method that I'm aware of, unless you want to attempt to 'milk' suspect males. As anyone who has kept clown loaches in a group setting in an aquarium knows, there is a definite hierarchy among the group. I suspect that only the larger more dominate females will become gravid in each group, possibly in some groups only one dominant female. I have a mix of sex, with a female that is currently gravid, and she's been this way for months. I can only take an educated guess as to what sex the others are.

 

[Coryloach]

I just came across an extremely interesting article from a Russian clown loach breeder. It pretty much answered the questions.

Some google translate was involved although I pretty much understand majority of the language....

This is the article:
http://aquaprom.su/soderzhanie_i_razvedenie1

I'll sum up what I understood from it.

He was breeding them artificially but he said he could not get viable eggs unless the females were at least 7-8 years old. His early failures were due to that.

The females are wider when viewed from above than the males(pretty obvious in my gravid female, ha, ha)

The pelvic fin in males is way more developed than the females, i.e. bigger

The distance between the pelvic fin and genitals is larger in females than males....if one manages to measure it....ha,ha

He said that unlike popular belief, adult female clown loaches develop more eggs and the eggs survival is greater if fish/eggs are kept at 24-26C max. This is pretty much in line with other scientific literature on the subject I've read.

Also, from same breeder but different article, eggs hatch in around 18 hours, in a day the babies accept food. In 2-3 days they develop 4 black stripes, eventually one fades....Water they were kept in had GH 8 and KH 4..

In relation to the pelvic fin. See on my picture below. It is pretty obvious the male has bigger pelvic fin!!! Top one male, bottom female, as I thought initially.....

 

[RD.]

Interesting, I'll have to check mine later when the lights come on.

 

[Coryloach]

Interesting, I'll have to check mine later when the lights come on.

I've been looking all day. Damn pond, impossible to see mine well from the side

 

[RD.]

LOL, yeah that, and how well are Russians to be trusted these days?

 

[RD.]

After spending some time on google, and viewing my CL's, I believe that this Russian breeder is mistaken. I see no difference in my group, and from their overall behaviour, shape, and size, I have to assume that at least 2, if not 3 of my loaches, are male. That, and overall there is still a lot of confusion when it comes to C. macracanthus, including the fact that the two strains in the hobby, Borneo vs Sumatra, are genetically different - some stating that they may in fact even one day be considered different species. Which strain the Russian was commenting on, or others, is anyone's guess. The "hooked tail" theory is also just that, someone's theory, that has never been substantiated within scientific circles. Like yourself, I see no difference in the caudal fins on my fish. (Borneo strain)

I'm going back to my default, gravid specimens are females, all others are questionable. lol

 

[Coryloach]

This video below is the breeding trio of the same breeder, the pictures of which are on the link I provided. There are 2 males 1 females on the video according to him. What I see are two very slim males and one very slightly rounder female. In fairness, what I consider males in my group look that narrow and flat like the ones in his video. Mine are just extremely narrow when viewed from above. Females are a bit "plump".

What he said on the previous link is that the difference could be seen if fish are the same age, different sex. I am guessing in a tank like mine, some at different ages and sizes, its hard to tell for sure.

I've been staring at mine all day, hard to see pelvic fin differences but it is very obvious on my previous picture....

Here is the video of his 3 breeding clowns:

 

[Coryloach]

My clowns at the moment are exhibiting some weird behaviour. I have the info on my other old thread about "shadowing behaviour". I've been reading and watching the fish all day on and off.

 

[Coryloach]

On my image below I reckon(my opinion) I have two males and two females.

On the left side of the picture, 3 clowns, top 2 are females, bottom is a male.

On the same picture, to the very top right is one of my largest males. He is very narrow if viewed straight from above. He is not bony but not one bit plump. He was involved in chasing my largest gravid female only last night along with another male slightly smaller than him.

 

[RD.]

My last CL tank held I think 15 loaches (this was 10+ yrs ago), all approx. the same age, and I would assume had both males and females. I just viewed some of the various photos from that tank, and I still don't see anything definitive with regards to fin lengths or shape. The Russian sample size is way too small, as is your CL tank, to really come up with anything definitive.
Outside of seeing a gravid female, body shape is still probably the best way to determine m/f, as in your pics.