That's a big one to tackle IMHO
I have a recent post that talks about... one of my FW
tanks that has been running for years without any significant water changes besides the occasional vacuum (live plants eat the rest of the poop) , breeding plecos and guppies.
There's a significant bioload, however the tank is in the sunlight for most of the day and has a huge amount of gas exchange (big big circulation via powerheads, a momma of a HOB
, mag350 with biowheel) and big bio filtration.
Breeding freely and happily are 4 species of plecos along with an abundance of semifancy guppies. Baby guppies everywhere, have to net a big pile of them to sell every couple months.
I lose about 5 gallons minimum of water per week in this particular 70G FW
, and just top off. The water quality of the tank has remains superb. The water has a fresh springy smell to it. All tests are primo excellent.
So I must say this...
In general : Water chemistry is insanely complex, anyone who claims that they *completely* understand water chemist to the "T" may be disillusioned, and... water changes are still a fine thing to do IMHO
. Anyone looking back though history will see a string of ornery scientists who fight off anyone who disagrees with their theories. One might call this chronological snobbery.
I remember reading a dated, highly acclaimed medical piece regarding yellow fever.. it explained in detail how people "catch" yellow fever... from breathing damp vapor from standing water and mud.
They just forgot about the mosquitoes back then.
So what I mean is that we as people can get stuck in ruts sometimes and defend our rut without understanding fully the chemistry of the rut. I for one do not understand my particular rut with the 70FW. So I will not defend it too much.
That particular 70FW gup/pleco tank just happens to be thriving sans changes. My water chemistry, sunlight, tank occupants, substrate, filtration, etc somehow is working great with this setup. And if my fish are breeding like crazy and the baby plecos and baby guppies are chowing down happily and all tests say perfect then that's good enough for me. If someone needs to do water changes then that rocks too. I do them too.. it just depends on the tank, man.