I perform a 15 gal water change each week but thats only 5% of my total volume. Each month I'll change out 1 cup of carbon and GFO which is again pretty minimal for the system size. Ca and Mg I'll test once a month as they don't fluctuate by much and after a few years of 0 I stopped testing PO4 and NO3. Alkalinity on the other hand can really jump or crash on me so I have to keep a close eye on it. I use a Ca reactor and Kalk reactor and once or twice a week add a few drops of Lugol's Solution.
Ca 400 - 500
Alk 9.5 ATM
Mg 1400
1.025
78 F
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