Sex Of Black Phantoms?

[Bugdozer]

I got the first fish in my new tank today, five very little Black Phantom Tetras. In the fish shop there were about 10000000 of them in the tank, and every single one looked the same. They are all quite small, just over a centimetre in size, and there appeared to be no colour variation in any of them. When I got home I looked them up and read that the females have the red fins etc and the males are territorial. I don't recall seeing a single red finned fish in the tank at the shop. I also noticed that although three of the five seem to have established little areas of territory, the other two will still participate in fin flaring behaviour when confronting the ones lurking in the territories.
Does this mean I definitely have five males, or is it possible it's three males and two females? Does the red colour on the females not appear until they are older or should it be there already? If I do have five males, are the two who haven't managed to find a territory of their own going to be miserable? (It's only a 40l tank so there's not that much spare room for all five to make a territory.)
I worry they will be unhappy

 

[thereverendturtle]

Looking at my group, the males have very long dorsal fins compared to the females and are slimmer. The only fins that are red on the females are their pelvic fins. It is possible they are just a bit to young to sex, mine are about an inch maybe a little more. When I purchased them, they were about 3/4" or so and were sexable at that size.

 

[Bugdozer]

Looking at my group, the males have very long dorsal fins compared to the females and are slimmer. The only fins that are red on the females are their pelvic fins. It is possible they are just a bit to young to sex, mine are about an inch maybe a little more. When I purchased them, they were about 3/4" or so and were sexable at that size.

The problem also is I have no basis for comparison for "longer" fins! Some of mine have longer ones than the others but I don't know what the natural amount of variation is within each sex. Every fish at the shop tank looked identical in colouration that I could see. I think it unlikely that they would have a vast majority of just males.

 

[thereverendturtle]

Here is a page with a pic of both sexes.
http/www.seriouslyfish.com/species/hyphessobrycon-megalopterus/

 

[Bugdozer]

Thanks, although that doesn't answer the question about their appearance changing with age, I can honestly say that some of the fish in my tank look like both of those pictures depending on whether they flare their fins or not. The female fish in that picture is clearly older than any of the fish I have. I want a definitive answer to whether very young females have the red fins or not?

 

[thereverendturtle]

Yes, the females always have red fins.

 

[Bugdozer]

Yes, the females always have red fins.

OK, they must all be boys then! When I increase their numbers I shall make sure I get girlfriends for them.

 

[Bugdozer]

OK, two weeks later...
After feeding them a diet that included Tetra Colour Crisps, we've discovered that the gang of five are in fact two boys and three girls! One of the females keeps having a "fin-off" with the other fish and is perhaps a little gender unsure, but there are red fins there all right. I can categorically state that there was no trace of red on any of their fins when we brought them home and this has appeared over the last two weeks.

 

[thereverendturtle]

That's a good sex ratio.

 

[Bugdozer]

Further sexing problems with the black phantoms!
Remember the "gender unsure" female I mentioned? It definitely had red fins, no doubt about it. The other day it must have got into a little scrap with the boss male of the tank, because I noticed both of them had a bit of fin damage, and they are always a bit shirty with each other anyway. However, the "female" has now lost almost all the red colouration from the fins - they look nearly black, with just the tiniest hint of red still there. The appearance is changing to almost exactly like the regular male colouration - what is going on? It always behaved in a rather bossy male type way, now it looks like one! Are they wrasse in disguise?

Additional: look what I just found:

http/www.fishforums.net/index.php?/topic/65075-sex-change/

Additional additional! Look at the second to last post here:
http/fishprofiles.com/forums/Tetra_Talk/Black_Phantom_Tetra_/33644/