I'm not recommending such large water changes. It isn't always easy to get the temperature close, and there isn't any point for the most part, but provided your tank is well maintained it wouldn't do any harm.
Not only that, but did you know there could be a possibility of a pH difference from your tank water than your tap? You can check this out by checking the pH from a glass of fresh tap water, then wait about 2 hours or so and check your pH again. The pH would be lower, this is becuase the CO2 in the water will escape. That's why those expensive pH regulators require a CO2 to inject into your tank (I believe that is the method). Here I am quoting the following from
this site...
"One safe way to lower pH WITHOUT adjusting KH is to bubble CO2 (carbon dioxide) through the tank. The CO2 dissolves in water, and some of it forms carbonic acid. The formation of acid lowers the pH. Of course, in order for this approach to be practical, a steady source of CO2 bubbles (e.g. a CO2 tank) is needed to hold the pH in place. As soon as the CO2 is gone, the pH bounces back to its previous value."
my fishes are extremely happy and well cared for
So I guess you don't do large water changes. I wouldn't advise it either.
Totally nasty and uncalled for remark
Yeah, I'm sorry. But I KEEP ASKING for references to their statements, but I HAVE NOT SEEN ONE. As you can see, practically ALL my information have references to back me up. They're not coming from site owned by Billy Bob who setup an aquarium a month ago, but several reputable aquarium sites, some owned or run by vets.
The water does not control the nitrogen cycle, the bio-filter does.
Do you understand the nitrogen cycle? Here's a
link regarding it. The key word is BIO. Bio filter contains benificial bacteria. This is also on the gravel bed, decor, some in water, fishes gills, and even in the filter media. That is why we seed new tanks using gravel from an established tank or even use the filter media from an established tank.
It's just if these statements are so called "True" then why not prove yourselves? When you guys do your water change, do 90%. Or better yet, take your fishes out and put in a bag of fresh water. Yes, make sure the temps is the same and you apply the correct conditioners. Then take out all your water from the tanks and replace it with FRESH clean tap water and make sure the temp is the same and add the proper conditioners. According to everyone's statement, then your fish would LOVE the fresh clean water. Or if you guys live near Chicago, then I will be glad to do the water changes for you, becuase I would like this to be proven to me. Like I said, I LOVE to do research and since nobody has given any links or references proving any of your statements, then all I just ask is that it will be proven to me. I have several empty fish transport bags and a Python No-Spill gravel changer that I can bring. I have some dechlorinators also I can bring.
Any takers?
FYI...Here is a
site containing reports of how water parameters differ in various cities in the US alone.