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I know. I know. We've discussed the downsides of impulse buys in the past. Well today I went shopping to pick through a tank of twenty so that I might search for mixed species. In the end, I bought 12 more bumblebees to go with the six I already have.

But nearby was a tank filled with ! I had one years ago which I found as by-catch with . But never a mate was found. I lost that first fish, but here was a couple dozen specimens! So, on impulse, I bought eight.

They are thin and need bulked up, so I couldn't sex them by girth. But then I noticed one fish has larger pelvic fins. Is that a sexually dimorphic trait? I hope not, because I don't want a 7:1 sex ratio.

Would be fun to spawn these. Wish me success!

Cheers, Eric

What size are the fish currently?
Whilst my instinct would be to say yes it should be a sexually dimorphic trait, my experience has never shown enough proof. Generally we buy small immature fish and tend not to recatch them to study once settled and sexing becomes easy in their home tank.
Best of luck breeding them.
One hobbyist suggested to me that they bred for him in the flow of a spray bar return or hang on weir filter return laying their eggs on the aquarium glass similar to Corydoras although I have never tried a setup attempt in this fashion and could not confirm if their eggs are indeed sticky enough for this to be true.

Will be good to track them, I do see a rounded pelvic fin in the larger one, can't say if it's sexual dimorphism or simply growth/development. The great thing is you've bought a bunch of them and can hopefully record their development.

Jools

Fishmandavew wrote: ↑03 Oct 2020, 08:59What size are the fish currently?
Whilst my instinct would be to say yes it should be a sexually dimorphic trait, my experience has never shown enough proof. Generally we buy small immature fish and tend not to recatch them to study once settled and sexing becomes easy in their home tank.
Best of luck breeding them.
One hobbyist suggested to me that they bred for him in the flow of a spray bar return or hang on weir filter return laying their eggs on the aquarium glass similar to Corydoras although I have never tried a setup attempt in this fashion and could not confirm if their eggs are indeed sticky enough for this to be true.

These fish are good sized already. 60mm or more SL.

I've bred the common banjo () several times (https://www.planetcatfish.com/shaneswor ... cle_id=532) and I'm hoping to be as fortunate again. Those fish were egg scatterers; the eggs were very sticky, so I wouldn't be surprised if the person you mentioned found some eggs stuck to glass. My prediction would be that they found only a small percentage of the eggs, and the rest were scattered everywhere else in the tank.

In my experience, banjos need a little bit of height to the tank because they perform a vertical cycle of a dance while spawning. Considering the size of the new fish, I think they're large enough (or close to it) to start spawning once conditioned, but they are skinny and need to fill out.

As far as sexing, if I did get only 1 female (or male, depending on the direction of sexual dimorphism) in a group of 8 I will be frustrated. There were at least a 10 to 20 more specimens to pick from in the fish store. How could I get such a skewed group unless the holding tank was also skewed in its selection? Dang.

I don't recall my B. coracoideus having different sized pelvics, although back then I wasn't photo documenting my fish as much as I do today. As you say, I'll need to track them to follow the development.

Cheers, Eric

@ biassed sexratio, I once went catching Ancistrus in Uruguay. One person lifts a rock. The other is fast with a net and hey bingo 1 Ancistrus caught.

But they were all male, as females are not territorial enough to keep on a rock when is moves.

This could explain a bias in more species

Bas Pels wrote: ↑03 Oct 2020, 18:17@ biassed sexratio, I once went catching Ancistrus in Uruguay. One person lifts a rock. The other is fast with a net and hey bingo 1 Ancistrus caught.

But they were all male, as females are not territorial enough to keep on a rock when is moves.

This could explain a bias in more species

Yes absolutely possible. My observation was that I made the mistake of not noticing the pelvic fins while still at the store, so I cannot attest to whether the fish available had a skewed sex ratio, or perhaps I had a bias which artificially selected males.

For example, my priorities were to make sure I picked nice looking fish from the tank - I focused on getting fish which were (most of them) large, and also that I picked fish with the least evidence of starvation, and I also picked fish with high occipital crests. Perhaps that latter choice led me to pick more males. If so, then UGH!

Cheers, Eric