Water For Developing Eggs Of Rivulus Xiphidius?

[Denitrator]

Hello everyone, I have just ordered my first eggs of Rivulus Xiphidius and would like to know how to prepare the best water for the to develop. I am quite experienced aquarist when it comes to tetras especially Nannostomus. I would like to know how harmfull is carbonate hardness for  the eggs and for the fry. Would appreciate any experience with this, becouse I have noticed that recomended water is quite simmilar in some parameters (conductivity, pH) to some tetras from the same type of environment in the nature and these are sensitive to carbonate hardness. Does the same apply for Rivulus Xiphidius? Could someone tell me how much of carbonate hardness is ok for the eggs any fry and in DKH? 
 
Thanks very much for help and explanation