Dan Mercer writes Lagonia. He keeps freshwater tanks on very hard, alkaline tap water, mostly shell-dwellers, Rift Lake cichlids and livebearers. He has killed a few fish learning what actually works, and writes Lagonia to help people work with their water instead of fighting it.
I did not set out to specialise in hard water. I ended up there because that is what comes out of my taps: somewhere around 22 to 23 degrees of German hardness, calcium-heavy, pH about 7.2, with a little nitrate in it before it ever reaches a tank. For a long time I fought it. I bought the pH-down bottles, read about peat and RO, and generally treated my own water as a defect. It was a waste of money and it stressed the fish. The turning point was giving up and picking species that actually come from hard, alkaline water. My shell-dwellers bred, the snails grew glossy shells, and water changes went back to being just water changes.
That is the thread through most of what I write. I am not a marine biologist and I do not have letters after my name. My authority, such as it is, comes from years of tanks, a lot of test-kit readings, and a decent number of dead fish that taught me things the forums glossed over. I try to keep the two kinds of claim clearly apart: the plain chemistry and biology on one side, and “here is what happens in my tanks” on the other.
A few things worth knowing about how I write. I lead with the practical answer, because that is usually all you came for. I am honest about trade-offs and about the times I got it wrong, because that is more useful than a clean success story. And I have nothing to sell you. There are no sponsorships and no affiliate links steering what I recommend. When a cheap sponge filter beats a pricey canister, I will say so.
If you want to reach me, write to privacy@lagonia.org. Corrections are welcome.
Everything on Lagonia is general fishkeeping information based on experience and reading, not a guarantee. Livestock is living, and results vary with your water and setup. Go slowly, quarantine where you can, and check any medication against its instructions before you dose.