How to sex a Hypselecara temporalis, Hoplarchus psittacus, and Mesoheros Gephyrus

[Cichlidfever]

They a all about 4" , I was hoping I could look at them and tell, without taking them out the water? Do they have to be larger, or it just impossible to tell?

 

[duanes]

If all the same age, males will get larger, and a bit more robust looking . Males will get about 12", females 10".
At only 4" , they are a little young yet.

 

[Kevin@TUIC]

without venting you would to need compare each species to itself as these are monomorphic species. In all 3 species males and females will look similar with very minor differences when mature adults. males and females (of most central & south American cichlid species) can grow long fin extensions and even both sexes can develop a nuchal hump so even that is not a good identifier.
When comparing to each other they of course need to be the same age( to rule out size differences) then typically the only differences between sexes on these 3 species is overall adult size. Also, using wild fish for identifying versus captive tank bred strains is better. In the tanks we tend to breed the nicest looking male to the nicest looking females and continue that line creating a population featuring something slightly different looking whether its a color, pattern, or even size

 

[Cichlidfever]

Thank you Kevin, I do have two of each, however, they all are the same size just at them in comparison, they are identical, although, I do understand your information that you have given... Thanks once again