Water Softener question

["Ed Pon" <edpon@hotmail.com>]

I am using a Culligan water softener which replaces calcium ions with sodium 
ions to soften the water.  The tap water comes into the unit at about 120 ppm 
carbonate hardness and leaves  the water softener at o ppm(using an Aquarium 
Pharmaceuticals, Inc. Water Hardness test kit).  I quit using my reverse osmosis 
unit because of the convenience factors.  I have had spawnings from A. 
Pandurini, A. Nijsenni, A. Cacatoides, A. Borelli, A. Norberti, A. MacMasteri, 
A. sp. Rotpunct, and probably a few others that I can't remember at the moment.
My water source is not terribly hard to begin with, so I figured that I wasn't 
really putting very much sodium into the water.  Also, cichlids in general, seem 
to have a high tolerance for salt, with some species actually reproducing in 
pure salt water.  Anyway--I have been not been able to get an answer to a 
question that I have posed to various authoritative people in the cichlid hobby 
in the past.  The question is: do soft-water fish in general, and cichlids in 
particular, actually require a low carbonate hardness to reproduce successfully 
or is the requirement for low conductivity.  I know that some people measure 
carbonate hardnes, some measure total hardness, and others use a conductivity 
meter to determine the suitability of their water for breeding soft-water fish. 
Anybody out there have any opinions, facts, theories, etc?