FishNoob wrote in
:

so I wouldn't have gone for this - my ph is naturally low to start
with. In fact when I sent hubby (who is home from work because I'm
....
home with something that looks like "LITH" on the receipt - looks
like crushed porous stone - and instructions to put it in the tank

It's for raising the pH? It sounds like crushed limestone or something
similar. It will certainly raise your pH by buffering up your carbonate
hardness.

You should get yourself a KH test kit so you can monitor how much this
"LITH" is buffering up your water. For a planted tank you probably don't
want your KH to get much higher than 4 degrees or so. If you don't monitor
it the limestone will continue to leech into your water regardless of how
hard you want your water to be.

In my own planted tanks I try to maintain my KH around 1 - 2 degrees, but
results will vary depending on your water source. I use Kent cichlid
buffer keep my KH around 12 - 14 to maintain a high pH in my African rift
lake tanks, but most plants won't thrive under those conditions.