Water changes definitely work—don’t get me wrong. But I think we often overlook some important math. When you perform a 33% water change, you're only replenishing 33% of what was consumed during that time. The new water gets diluted into the existing water, which means each subsequent water change becomes slightly less effective. Over time, this dilution effect adds up. That’s why dosing macro and trace elements eventually becomes necessary. Personally, I believe this dilution is what led to the dreaded “old tank syndrome” back in the day—before automatic dosing systems became the norm.
I had AI do the math (any mathematicians out there want to verify this?)for what it would take to change 100% of the water in a system doing consecutive 33% water changes (keep in mind this does not factor time between water changes when more depletion of elements occurs) and this is what it came up with:
Great info Steve! Thanks!!