Sexing frontosa by size

Jag586

Piranha
MFK Member
May 28, 2012
1,234
36
81
st clair shores
So I moved my 15 frontosa to my 220 gallon tank from my 50 I was watching them explore and I fed them and all was good till I thought of poo I was suppose to sex them then move them, well my fronts size is like this
3 = 4"
2 = 2.5"
10 = 3-3.5"

One of the 4 inch guys is darker then the rest of all the fish they don't fight at all the three bigger ones kinda push around the smaller ones

Here's my question can I sex fronts by size alone? I read no... I read mostly yes. I want to end up with 2 males and the rest females so should I when they get say 4-5 inches sex them and just keep two males as the rest grow sex them and keep getting rid of males or .... Just let all be till they start to fight? I plan on any males selling / trading for smaller ones to grow out and hope for more females


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chopsteeks

Plecostomus
MFK Member
Jun 2, 2013
418
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61
Denver
In general, you can....but not accurate. Venting is really the best way to sex Frontosa. You have to wait a while to vent all of them as they are in that borderline size. But with Frontosa, you have time before these fish become sexually mature....so no worries about aggression.
 

neutrino

Goliath Tigerfish
MFK Member
Jan 22, 2013
2,396
2,627
179
Mid-Atlantic, US
Sexing by size is not at all foolproof. Generally ime in a decent sized group growing out you can pick out a few males and females at opposite ends of the growth spectrum-- a few larger, faster growing fish that generally turn out to be males and a few slower growing and smaller than the rest that will usually be females. This is a generalization and it's possible to have an exception. But even more so, in between the largest and smallest it's easy to get it wrong. Fish in the middle can turn out to be either one, even more so when you're still in the 2.5-4 inch range.
 

poppalina

Gambusia
MFK Member
Sep 26, 2010
669
27
18
Boston
You have more than enough tank space for them, I would grow them all out till the aggression starts if ever. The males shouldn't be sexually mature until about 8" so you have plenty of time. Venting them is the only accurate way to sex them, however behavior can give you clues. Your fish that is darker than the rest is probably the boss and possibly male.
 
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