How do i get my frog into the "mood"???

I had african clawed frogs (similar to ADF but larger). they bred EVERY time I changed the water. We had eggs stuck all over the glass nearly every week. You could hear the male croaking (the only time they made noise) then the eggs would appear in the morning. I was only a kid and my mother would yell at me calling my frogs "piggy". lol
 
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