Using a lot of stone around the pool, has a waterfall and weeping wall. The corrosive effect of salt (SWCG) on the rock and concrete has us concerned. If not a chlorine tab feeder then what should I look for?
Staying away from a SWCG is not going to keep you from having problems with "salt" (chloride ion, Cl-). Any pool that uses chlorine as it's disinfectant will, by it's nature, build up chloride over time. This comes not only from the use of chlorinating products (bleach, dichlor, trichlor) but also from the use of muriatic acid (HCl) to adjust pH.
Looking up your evaporation and precipitation data
HERE (assuming I got your location right), you can see that you have an average annual precipitation of 38" but an annual average evaporation of 57". So, you can reasonably expect to lose 19" of water in an uncovered pool. That's not too bad (especially if you use a solar cover to control evaporation) but that also means that you will, on average, build up chloride in your pool water. In some of the more extreme climates and with new pools that typically use more acid and chlorine in the early years, pool owners have easily seen their chloride values go up by over 1000ppm per season. So, as you can see, it will not take too long before your pool becomes a salt water pool, whether you want it or not.
As for stone degradation, that is a concern for soft limestone materials, travertine and, from user reports here on TFP, we see that Texas flagstone seems to be more susceptible to salt water induced spalling than in other regions. Concrete should not be an issue because your decking and mason subs can use concrete mixtures that are formulated for salt water exposure. True stones and boulders (granite, etc) used in the construction of rock waterfalls should be fairly stable to salt water. Stacked stone weeping walls should also be stable as well (although calcium scale will definitely plague you on that one). If you give us more information on the construction materials you will be using, others in the Texas area may be able to guide your choices to higher quality materials.
At the end of the day, it is a good idea to consider sealing stone materials that will be constantly exposed to water. There are many different sealants on the market (DuPont, Dry Treat, etc) that are designed specifically to infiltrate soft stone and seal the pores against water infiltration. This helps a lot although it can add significantly to the cost of a build if there's a large square footage area of stone to be sealed.
Good luck,
Matt
