Small breeding tank wat to do

[BoabMac63]

I finaly managed to sqeeze a 20g long under my 120g i have 5 guppies in atm i would like to get sumtin easily breed bit can be sold like kribs or sumthing and with the guppies breedin in the tank aswell problem is it doesnt get much light but it does get light from my window its has a 350lph filter on ot aswell sand bottom