Limestone and GH

[laurw]

DH and I have been adding chunks of cured plaster of paris (aka 'pH pills') to our pond from time to time, especially after large rainfalls, to harden our pond water and it works beautifully when we keep up with it.

But forget for a week or two, the GH plummets and all the snails disappear.

I understand that additions of natural limestone rock are a good longer lasting water hardener.

Can anyone corroborate this? How much should we add to an 1800 gal. pond with a low/moderate fish load?

[bunny56lbc]

I was always told limestone wasn't good for the pond , so I never put any in.
bonnie

[laurw]

Really?? What's wrong with it?

[models916]

Where is your PH? Keep it at 7.5 and all will be fine.

[PondmaninAL]

Yeah, what is wrong with limestone? For those of you who have bought Wal-Mart water plants, they use crushed limestone in those bags to weight it down.

Happy ponding,
Scott

[bunny56lbc]

We have Limestone rocks in the creeks around here . A friend told me to never use them
because they will eventually poision the fish . As far the plants I have no idea if it will hurt them or not.
bonnie

[laurw]

I read online that in areas with acid soil, pond farmers actually shovel crushed limestone over the surface of the pond to make nutrients available in the muck and thus eventually harvest a bigger fish load.

*scratching head*

OK, I don't know what to do now.

[Jonna]

Limestone is alkaline so in areas where there is limestone laying around the water is also probably pretty alkaline so adding more would be bad.  But, in areas where the water is soft and the soil is more acid then adding limestone (which you probably wouldn't find laying around) would bring the GH up and make everything more neutral.  Does that make sense?

Here in the desert where there is limestone laying around and the water is very hard I wouldn't put any in the pond.  But up in the Oregon forests where the water is probably pretty soft and the soil is more acid, adding limestone to a pond might bolster the GH. 

Just a guess.

[JoshS]

I have limestone in all my ponds and have for years.  No problems.  If anything, it helps prevent pH crashes.

[bunny56lbc]

Limestone is alkaline so in areas where there is limestone laying around the water is also probably pretty alkaline so adding more would be bad.  But, in areas where the water is soft and the soil is more acid then adding limestone (which you probably wouldn't find laying around) would bring the GH up and make everything more neutral.  Does that make sense?

Here in the desert where there is limestone laying around and the water is very hard I wouldn't put any in the pond.  But up in the Oregon forests where the water is probably pretty soft and the soil is more acid, adding limestone to a pond might bolster the GH. 

Just a guess.

It make's sense to me! I've been told the water is hard around here , several people I know have water softners.

[karen J]

Unless you are raising certain patterns of Koi, general hardness (GH) is pretty meaningless. My water comes from a well and the hardness is literally off the charts.

What is important is KH- Carbonate Hardness. KH is what buffers the water and prevents a pH crash. Limestone can be used, as well as crushed Oyster shells. Or Baking Soda. The myth that using certain kinds of stone in the pond comes from the fact that the pH may be naturally raised in that situation... but the trade off is better buffering. pH crashes kill fish, not consistently high pH. It's more important that the pH is stable, and buffering the water accomplishes that.