It's pretty hard to sex these frogs when they are small but once they reach about 10 months old it will be easy.  The male frogs are usually smaller than the females and less pear shaped, they have black patches on their inner arms called 'nuptial pads' which are used for holding on to the slippery female when they are mating.  Females grow much larger and have a small appendage between their legs called an 'ovipositor' used to deposit eggs.

Female Frogs:

• Have a small 'tail' between their legs, this is the ovipositor which is used to deposit the eggs
  
• Are much larger than males, growing as large as a clenched fist and are more pear shaped
• Do not have black inner arms like the males, but might have some black colour on the inside of their hands
  
• Only click during mating, they don't sing

Male Frogs:

• Have dark patches on the inside of their arms.
• Are smaller than the females, and only grow to 5  inches
  
• Often make a scraping croak in the early evening or when excited
  
• Will swim around trying to hold on to other frogs
  
• Do not have an Ovipositor
  

Mating can take place anytime; however, is more common during spring time and often occurs after water changes with fresh, cooler water as this resembles the rainy season. Four matings per year are reported for compatible couples. For a pair, 5-50 gallons at a depth of 8-9 inches is adequate.  When frogs detect no other activity going on around them, which is usually at night, mating takes place. The male will grab and hold the female around her waist and the pair will swim around like this for hours.  The pair will communicate during mating (check out the sounds page to hear this).  When ready hundreds of sticky eggs will be produced during a 3 to 4 hour time period.  Mating resembles a dance between the frogs from the bottom of the tank to the top of the water and over again. 

A pair of frogs in 'Amplexus' releasing eggs: