At what size can you sex a bristlenose?

Think Ive just made a mistake : /

Ive been trying to get hold of a female for a while and being frustrated with not finding any in London I had one couriered over. The seller said it was '6cm+', since my male is less than 8cm at about a year old, I assumed a specimen longer than 6cm with no sign of bristles would be a female. The plec that arrived today is tiny, I cant measure it without stressing the animal but I would guess a little under 6cm and very very slight. Probably less than half my original plec in volume. edit: just measured at about 5cm

Is there any more than a 50/50 chance that its female? If it does turn out to be male will it fight with my original plec? The tank footprint is 45cmx120cm with one large pile of driftwood at one end.

Hard to give an answer without knowing what BN your talking about.. There are many that develop very slowly and some that don't. I have had males with other males that show no bristles until it was moved to a different tank as it was hiding from the more dominate male in the tank.

Its a common albino bristlenose

I start noticing mine maturing at around 2.5" (6 cm).. I have raised many of the common BN's and if kept in good water conditions with plenty of hiding spots I'll see a few bristles form in the middle of there head at that size with the dominate one getting more than the rest.

Rats thats pretty much what I figured. Not sure whether I'm more annoyed at the seller or myself.

it is possible a bit before then too based on body shape but it is a bit hit and miss and can depend on when the fish last ate.

Right I guess I feed it up and keep my fingers crossed over the next few months. In the mean time 'it' clearly needs a unisex name (suggestions welcome).

What difference in shape should I be looking for?

there are very clear diagrams in my book. see the link in my signature

Not sure what others think but on my young ones I can often see the red patch behind the head quite early (about 3cms +). I assume these will be males but I don't confine them in any way to check what they actually become. Might be an interesting thing to set up a tank for these fish?

June, My female Albino's often have the red/pinky patch too...

Can you take a picture Ony?

june wrote:

Not sure what others think but on my young ones I can often see the red patch behind the head quite early (about 3cms +). I assume these will be males but I don't confine them in any way to check what they actually become. Might be an interesting thing to set up a tank for these fish?

In my experience with albino bns, individuals with the red/pink patch behind the head are usually male, too.

Its still quite shy and difficult to photograph but I'll have a go tonight with a nice bribe. The seller has gotten back to me and said that his bristlenoses are all quite small especially the females. There is nice bristle growth on others the same size so hes pretty sure it is a girl.

Ive named it George

I often find that males generally start to get the little tiny bumps around their nose anytime after they reach 5cm. But it's a hard thing to determine as some can be late bloomers. I tend to check them by waiting for them to attach to the glass and staring hard at the nose, or getting a camera to take close up/macro shots to get that little bit closer.
Body size is usually to hard to tell at that size but females are generally plumper. And the red patch on the head can go either way, my albino female is about 9-10cm long and she's got a fairly bright red patch, though I do find males patches can be much brighter. Either way I wouldn't go off the patch.
Look at the body from above (or below) and pay close attention to the nose. A picture can always help though :P

Hello,

I've got an albino bn about 3cm long, where abouts on the head is the red bit, on the underneath (and therefore a doddle to see!) or on the top side of the fish? Not that I think it will help sex it but just curious....

My 5 cm one has got the little lumps starting on his nose now, have to be very close to see them though!

heres a pic i found that shows the red (more like pink) patch on the top of the males head. And yes i have seen females with the patch too...








this is not my pic and i apologize to the owner if i have used it without consent

Great pic! Thank you for that.

Now I will spend ages scrutinising the top of my abino bn, in addition to checking the developing bristles on my first bn!

Su