I moved from PA to Myrtle Beach about a year ago.
In PA, My water PH really didn't seem to change while in the tank. Down here, I noticed that my tap water starts out 7.6 but by the time I do a water change it's down to 6.2-6.4. My tanks have a lot of plants and the rest of the parameters stay pretty constant.

I tested my hardness and found that my carbonate hardness is less than 50 ppm. Is this why my PH crashes so quickly?

Where I moved from, we lived in an area of large limestone deposits. I imagine that this is why PH stayed constant.

How important is this to my livebearers?

I should add that my Xiphophorus couchianus are as prolific as ever, but the Xenotoca eiseni fry don't seem to survive as well as before.

Harry Knaub

Hardness has never been a big issue for my fish. The only fish that I have ever kept that were picky about hardness were Discus. If your pH fluctuates too quickly it can stress the fish which explains your X. eiseni fry dieing off. I would raise it a little bit to help hold the pH and keep stress low.

My pH is neutral with a low KH. I had no luck at all stabilizing the pH until I stopped focusing on pH and started focusing on KH. I use Tufa Rock, Texas Holey Rock, seashells, crushed oyster shell and aragonite in all of my tanks now. These methods provide gentle buffering, as opposed to adding commercial products or baking soda. I do avoid doing huge water changes as well, opting for smaller, more frequent ones. Good luck!

Melody
That confirms what I was thinking. How do you use these products, just add them to the gravel. If so, at what rate. I have noticed that the PH will drop in just a week or so. Even though I didn't test for hardness in PA, the PH held above 7.0 rather consistently whether the water was fresh or in the tank for a month. By the way the fry did very well the whole time I had them in PA.

Harry Knaub

I'm not exactly one for measurement, for aquariums or cooking...LOL. It depends on the parameters you're starting with anyway - you have to play with it to find what works for you.

You can often find Tufa Rock in fish stores. It's attractive and great for plants that attach their roots to objects. I have varying sizes of Tufa, Texas Holey Rock and seashells scattered in all of my aquariums.

The crushed oyster shell is great because unlike coral, it dissolves so you know when it's depleted. The small pieces dissolve more quickly than larger objects as well. I put that into my HOB filter cartridge, box filters or in a media bag.

The coral with aragonite or aragonite sand can be used as a substrate, but it does lose it's buffering power eventually.

I also add a dash of seasalt and calcium montmorillonite clay with every waterchange. Just enough to add minerals, since fish absorb minerals from the water column as well as the diet.

Guppies can be highly adaptable (unless they've been improperly bred to a point that they can't cope with anything). The fish born into your new water parameters should thrive, even if your current adults continue to struggle. I've successfully kept all of the species you've mentioned in my current water parameters, if that reassures you at all.

This is another thing I do:

Box filters are under $10.  I fill them up with aragonite sand, coral, oyster shell, sea shells and snail shells with a little floss on top.  The water flow keeps the contents disolving at a good pace.   It's a fantastic place for beneficial bacteria to thrive too.  I change it out every six months or so.

I like the idea of placing shells in the HOB filter, since the tanks are already up and running.

Thanks