I'm new to this water chemistry thing but trying to get as much of a understanding as I can. One question I have that I'm having trouble getting a clear answer on.
Will adding ag lime to already high pH water increase pH even more?

Why are you thinking of adding lime if your pH is already high?

My alkalinity is OK for now (close to 50 ppm),my pH is 8.4-8.8 depending on the time of day. Mostly lm just filling my head with all the info about water quality I can. And I understand that alkaline water and alkalinity are two different things. My local fisheries biologists says that the high pH must be do to lime in the water source. I'm not sure he's right. Just looking for right answers!

See these fact sheets from SARC

https://srac.tamu.edu/viewCategory/25

Optimum alkalinity is about 200

Thanks for that link

Yes and no. It all depends on what ag lime you use. If you were to use dolomite lime the PH will rise still. If you use calcium carbonate it will bring the PH down to 7.2 - 7.5

Why you may ask? its because calcium carbonate has a buffer capacity in it to balance the PH and keep it stable. The extra magnesium in dolomite lime will not allow the PH to drop to keep it high. There is very little buffer capacity in dolomite lime.

You can't screw things up with calcium carbonate lime. Only if the product is a very fine mesh and has natural calcium hydroxide in the source.

Cheers Don.

Try this one about your question


https://srac.tamu.edu/serveFactSheet/112

Don, your saying the above about dolomite and calcium carbonate always confuses me as to how, chemically, the outcomes stated could occur.

Pure Calcium Carbonate has a pH of 9.4. Dolomite is mainly Calcium Carbonate, along with varying percentages of Magnesium and other minerals. Magnesium Carbonate pH, more particularly the most common form of salt named Magnesite, is more unclear, is insoluable in water, but if made soluable has a pH around 10+.

Both Calcium Carbonate and all forms of Magnesium react with, and "buffer" acids. Magnesium Carbonate, is most commonly called "chalk".

I guess what confuses me is that both Magnesium and Calcium Carbonates require extreme heat, or an acid to change forms. Buffering, or being a "buffer" refers to the ability to neutralize an acid, so how can Calcium Carbonate "lower" a higher, more alkaline, solution?

Interesting reading on the needs and relationships between calcium, magnesium, pH and alkalinity, though geared toward saltwater reef growers... A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH

Not sure about the differences in Mg and Ca alkalinity. The only difference I am aware of is the differences with water hardness between the 2.

How do you tell which is which? My local source of lime is a rock quarry that provides snow white Rock and dust. Another place not too far from here has blue colored rock. Is there a difference between the two besides the color?


Also some observations I've made over the years. The grass along the side of a gravel road is the greenest and when I was a kid I fished gravel pit ponds and the water was blue/green and the fishing was good! That's a lot of lime!

That does seem a bit high... Just like low PH to high and your fish will die also.... I would say at 8.8 PH your pushing it... IMO best swing to be in is about 6.5 to 7.5... course I am sure some of it would depend on type of fish you have...

My pond is in lime country also and my PH is only about 6.7, but I do have a lot of pines around my pond.... as I slowly get rid of them I am going to see where my PH ends up I think it will rise some...

RC

The quarry should be able to tell you the average mineral compositions of what they sell/excavate.