Fish do need specific parameter ranges. Try keeping wild caught Altum angels in your tap water and you will very quickly learn this first hand. Or put a few Rift lake cichlids into soft water with a slightly acid pH. My tap water is basically neutral pH and soft. But to keep my Altums it would have killed them. My first imports went into a tank with a pH of 4.2 and TDS about 25 -30 ppm. I spent 6 months acclimating them to live at 6.0 and about 60 ppm.
As for every few days replacing most of the water in your tank, that may help. But what do you do when you have 20 -50 tanks and are keeping fish for which you modify some of the parameters? Do we think that a public aquarium with a 100,000 gallon tank does water big water changes?
And what do you do when the parameters from your tap change? They do change, and we are often not aware of this. if nothing else many water systems experience seasonal changes in parameters. When they have to flush out a system they often change the TDS and pH. When I began in the hobby my well water tested at 6.4 and KH was 6-7 and KH was 4-5. And then about 20 years into the hobby a friend came by and she stuck here TDS meter into one of my tanks and informed me my water was 83 ppm. That is a a few degrees lower than the old KH and GH tests indicated.
A few months back I noticed that the parameters in my Altum tank were drifiting up much faster than they had historically. I also had some odd readings at the start of this summer when I set up the bio-farm to cycle filters. It turns out the tap parameters had changed again. My pH was up a few .1s and my TDS were back up to the 105 ppm range. But, I now have TDS meters and a continuous digital monitor on my Altum tank which I can also use to test the chning water params. I bactch the changing water parameters based on tank readings right before setting up the changing water. Normally I need to ower both the pH and TDS some. If I miss a weekly change the correection needed is a bit more.
Some fish are naturally adapted to seasonal parameter changes. They have live in water which regularly experiences such changes every year except when mother nature acts up. To trigger my plecos to spawn when they are being sturrborn, I do a dry and rainy season. Not only do I change the TDS, but over 2 -3 days I drops the water temp from 92F (33.3C) to the 76F (24.4) range. From there I set my heaters to about 82F (27.8C).
Moreover. I was taught I can change the pH in my Altum tanl by 1.0 in 5 minutes and the fish will be fine. I have done this on several occasions over the years. When I got my first altums from a small scale imported I got them fdrom his fish room. I watched him drop the pH in one tank by 1.1 and the fish never seemed to notice. This went against everything I had read or been told. But for this species it worked just fine. I would not be inclined to do this with other fish.
So much for the idea that what all fishj need is stable parameters. What trhey need is the right parameters which are not single numbers but a range.
One last observation about doing big water changes regularly as suggested. If you are on municipal water, you probably pay for your water. Mine comes from a private well. But I pay for the electricity to pump it out of the ground. And then I pump water into and out of tanks, more electricity. Unfortunately, my electricity provider is the most expensive one in the country unless one lives in a very remote area with a small number of users. And I cannot use buckets as there is too much water involved and too much distance it has to travel to be removed and replaced. Right now I have 25 tanks going in two buildings and 5 rooms. My smallest is 5.5 and my largest is 150 gallons.
Next, it is far more than 1 in a million whose tap water is not great for keeping fish, ir even drinking sometimes. Here is a survey taken in the Phoenix, AZ area of homes which use water softeners:
Views of Water Quality are not materially different between those owning Water Softeners and those that don’t. This is likely due to the fact that eight-out-of-ten state they primarily use them to Reduce Water Hardness and not to Remove Contaminants.
One-quarter of all homes surveyed have a Water Softener, with penetration approaching four-in-ten in the Growth area, almost two and one half times greater than in the Established area. Reverse Osmosis system ownership follows this same pattern.
Water Softener (and Reverse Osmosis system) ownership significantly increases with income to nearly half of all households having Water Softeners in the highest income group.
from
Water softener survey
In 2004 there were about 3.2 millon people living in the greater Phoenix area. Even if this include double the amount of folks in the survey, and homes average 5 people, that still means 320,000 homes. the survey says 1/4 of homes have softeners. That would be 80,000 homes. So much for the 1 in a million thought. Oh well, back the the drawing board, maybe?
https://www.macrotrends.net/cities/23099/phoenix/population
A 2021 survey by the University of New Hampshire- Casey School of Public Policy asked several Qs. One was is the earth flat and "10 percent think the Earth is flat."
Conspiracy vs. Science: A Survey of U.S. Public Beliefs
edited to add the survey info and then to fix the link
