Water Source Change, How to Manage Transition

[DJW]

Some of that might be caused by evaporation. Calcium carbonate is barely soluble in water, and when it does dissolve it does so very slowly in the ground over a long period of time, so that when hard water comes out of the ground it can be at or near saturation.

CaCO3 is unusual. Most solids get more soluble as the temperature of the water increases, but CaCO3 does the opposite. We take cold well water and warm it up, which brings the CaCO3 closer to, or beyond, saturation, and then over time as the water evaporates the concentration increases just enough to drop some out of solution. I'm speculating some here... carbonate chemistry is pretty complicated stuff because of the way (bi)carbonates interact with atmospheric CO2 and other acids or minerals in the tank.

I get a white film on the bottom glass too. I have assumed it was mostly bacterial film but some of it could be a precipitated mineral. When I look at it under the microscope I usually find protozoa there, so I wipe it off with my fingers or a little sponge while holding the siphon right nearby so it gets drawn out.

[RogueDiscus]

Thanks Dan. Always appreciate your insights. I do have very hard well water, around 450 ppm this time of year. I definitely get a fine grain particulate deposit, in addition to the usual film. I like the evaporation idea. Makes me think the consumption of the carbonates by the bio-load may not be too high, but I do like the idea that I have the natural buffer.