Greg Dalton wrote in message

I was curious about using some rock that I've had for 10 years(in
cichlid tanks)...
Its cave rock. My LFS has highly recommended that I NOT use it in the
plant tank because the water would leach minerals and stuff out of it
and harden my already hard water. I used a large portion of RO water to
soften my water a bit and the LFS store guy added that it would increase
the leaching even more...
Anyone got any ideas? I'm looking at going with Lace rock if it turns
out that plants dont like this rock..

Hi Greg,

You can use pool acid, eg HCL, muritic acid, to test the rock for
cabonates. Foam= carbonates, mostly CaCO3.
I use rocks that have limestone and other pieces of shell etc in them
without issue, but if you plan a lot of it, it might cause some rise
in KH/GH.

But soft water or RO water was and is not needed for a nice planted
tank, that is simply put, one of the largest myths about planted
tanks.

Plants want CO2 and nutrients, not soft, poorly buffered nutrient poor
water.

Frequency of water changes also plays a role here. The more you do,
the less it will effect the tank. CaCO3 in a big block is very slow to
dissolve.

RO water taste good, but it's not useful for plants, perhaps for a
very few fish species, but it causes more problems and work for
planted tank hobbyist concerned with the plants themselves.
My GH is 25, KH was 10, plant did great, eg to the level of Amano's
pictures. So................

Planted tanks need at least 3 KH and GH. Why take it out then add it
back again? You can blend it with tap water to get whatever KH/GH you
want for your fish.
Tap water is full of plant nutrients in most cases.


Regards,
Tom Barr