Does a slate of green limestone affect my aquarium water? i have soft water and low ph. will it change it?

Answer 1

Slate and limestone are two different things.

Limestone is a calcium carbonate, so it does have the potential to raise you pH. If it's in a single large piece, it may continually dissolve, or it may encrust with other minerals in your water which forms a "crust" that prevents further dissolving.

Slate, if this is the type sold in pet stores, shouldn't affect you pH at all.

Are you trying to change your pH, or wondering if the rock will change it from what you have? Unless the pH is very low (below 6.0), your fish should be fine, unless you're keeping something that requires a high pH. If you need to make the change, a mesh bag of crushed coral placed in your filter will provide more surface area and will do a better job than a single large rock. But unless the change is absolutely necessary, you're better off to leave the pH alone, and just spend a little extra time allowing your fish to acclimate to the pH as it naturally exists in your water.

Answer 2

Yes. and Yes.
Limestone is Calcium Carbonate and can alter pH and kH when dissolved. Also keep in mind that limestone is partially soluble in neutral water and will readily dissolve in low pH. Also, if the green is natural, as in not dyed, it is a result of minerals present in the limestone, probably copper, which is extremely toxic in an aquarium.
However, if you think the limestone looks nice and the fish like it, I would recommend you seal it somehow. Resin or something like that should work fine. Don't use things like clear nail polish since it could erode over time and poison your fish.

Answer 3

Of 'course it will-it's like pouring drano into your water at a very light rate.Algea growth only speed this up. The alkalinity can be managed -but the rules are much more complicated.