OK I have a few minutes
First of all lets agree on our terms -
Dimorphism refers to size and shape differences (like fin or ray length for example)
Dichromatism refers to color differences.
The regional variation of flames specifically adds somewhat to the confusion, but IMO not enough to throw out sexing by color
There are going to be fish displaying colors in between male and female because they don't change over night. If a fish is starting to show male coloration, you can expect this fish to behave like a male as the male behavior precedes the color change. This fish would be easier to pair with a female.
It is my habit to recommend juveniles to people who want to have a pair simply because I worry that they'll make a mistake basing their decision solely on dichromatism. So in a way I agree that there is a big chance for error. However, once you "get it" and know the difference --- it becomes rather easy.
Until now I hadn't run into people desiring a large robust breeding female. I don't know exactly how large females get, but since 3.9 inches is considered maximum length for a male and the females are always smaller, I wouldn't expect to see one much larger than maybe 3 inches- if they do indeed reach that size (?).
The sexual dichromatism that is easiest to "read" on flames is the blue on the tail & anal fins. The females and juveniles only have a scant amount. Once you know what you're looking for, they are quite easy to sex - but as I mentioned before, photos can be deceiving.
Regarding the blue, a female will only have about one fourth to one third the amount of blue that a male has---- that's if you were to measure horizontally. Naturally that's relative to each fish's size. In the photo on this thread of my female, you can barely see her bit of blue outline.
As for the juveniles, it has been shown that young juveniles can become male "early". So one would assume they would become female early also. So while normally a tiny flame wouldn't be male, it is possible.
Here's more about the study I sited above - looks like Henry C. Schultz gained access to it in its entirety
To me, it's apparent from the study that if you can simply select a male and a female and pair them, it is cheaper (fewer fish deaths), quicker & easier.
I would like to point out that in the study, they relied on dichromatism as a means of determining sex. And, though I don't know for certain, I assume this was confirmed by dissection.
On to of all that, we're not even talking about fish that have fixed sexes, but fish that have show the ability to change. Thus, like so many other fish that are more likely sexualy monomorphic, I'm more prone to relying on behavior, size at introduction, and interaction between the "proposed pair" and ultimately only once the pair breeds and produces viable eggs do I know that the pair IS a pair.
But a lot of time & effort can be saved by simply selecting 2 fish of the correct sex when that is an option.
but take a look at Danfirth's picture post. If all flames showed dimorphism to that degree, well I'd say we're onto something. But look at the 2 I've started with, both of which are "inbetween" those two extremes.
Actually I believe those fish are both males, you may have missed a post or two where this was discussed
Let's look at Pearly Jaws, which depending on which source you believe, males have black spots on the lower jaw. My pair, and those pairs of many others, neither fish has these black spots. I think the "blue" and "barring" of flames may be akin to the Jaws, where it *may* be a helpful indicator but is most definitely not reliable.
