I'm always refer or keep thing nature as much as possible for my aquarium. I setup my 125G aquarium with lot of driftwoods and lot of plants (anubias, java fern, java moss and amazon sword) and stock with 125 Exodon, I'm running dual (2x) Fluval G6 system, UV and 2x Aquaeons 700 Circulation and only feed my fish 1 time a day (might be 2 times on weekend), with lot of driftwood in my tank it reduced my tap water PH from 8.2 down to 7.4 without peat. So far, every week water test result showing 0 Ammonia, 0 Nitrite and very little Nitrate (almost none exist or showing 0 compare to the color API test chard card). Our California state has been in shortage water for last few years so I don't want to waste our water by changing 30% water every week if I don't need to do that, I'm only clean my mechanical filtration every 3 days and refill my water weekly. So my question is as long my water stay stable I don't need to do weekly water change right?