Who Gives A Fish Forums

I'll keep doing the water changes then.
I've got an auto water change setup from a rain barrel, but the auto top off is still from the mains supply. If I can work out the daily evaporation loss, I can set the auto water change to replace double that amount with rainwater, that should give me a good ...

1300l dirt/sand planted tank here, 150l sump.
My tap water's a real challenge - PH 7.8/8, KH11, GH20.
I'm trying to avoid another RO unit, so I've been using collected rainwater to hit my target of PH 6-7, KH 2-4, GH 4-6.

I've been doing water changes for a few days now, and I've managed to bring ...