How long bettween water changes should I wait to do another one? Nitrates were at 80...I did a water change of 42g in my 125g tank and now its at 30. How many gallons should I take out next time? Trying to get my Nitrates lower.
That's a 1/3 water change, I'd wait 3 or 4 days , testing daily and tracking the results. If it starts to head up again, I would do 15 or 20% water change.
Please, other opinions, but even with nitrates at 80, you want to try to change it gradually.