Hi.Danny.......##
Sorry,man-I haven`t seen your question!!!
I have no idea at the moment how to sex them,because I have got mine since 4 weeks now and they are not adult yet!
The is nealry no way to sex a not fully grown snakehead..........!
To get a couple it is allways better to buy more than 2..........
I always buy 4-6 juveniles or subadults!
Snakeheads do not like it when they cannot chose their partners!
They have to find a partner by their own.......otherwise they will not harmonize and if they do not----they maybe kill each other!
So,allways get a group!!!!!!!
About the parameters they prefer:
They live in a lttle stream in rakhine state Myanmar.
In the hottest season the temperature is not getting higher than 25°C
The coolest months are from December to February-temperatures down to 15°C
So ,they are suptropical species-not tropical!!!
Recognize that!!
They need a good ,strong water circulation,because the live in a flowing stream.
I have a 6000 liter circulation pump in a 120 Liter aquarium..........they like it!
They prefer a ph of about 7.............
Hope that helps!
Pascal