You are right to ask questions. That’s the point. If you said, in my experience fish grow larger when you do water changes and this is repeatable over many years, my response would be. Hmm ok, I wonder why that is.
[ it's not just my experience tho. The vast majority of the tropical fish industry has had the same results.] My second question would be ‘but does a larger fish truly (think about this) mean it is any healthier?
[I don't believe that you can get a healthy FAT fish while you can get a healthy large fish when given ideal conditions with no human interference. There's no better example of this than in humans and farm raised chickens for meat. ]If we could categorically say that larger fish means longer life, healthier fish then I’d be interested in finding what the mechanism behind that actually is. [
What I don’t like to see is this completely unproven notion that hormones and/or nitrates are the primary cause because it is completely unproven. You could present this as one hypotheses but it still needs testing.
[You're right that there doesn't seem to be a lot of study on this with tropical fish but there has been a lot on hormones on other species of food fishes in which the results can be, and imo should be, extrapolated into the tropical fish databanks. ]
I did state that I’ve had success keeping fish with tanks that received massive water changes and also with tanks that received none, so in my experience water changes do not define an aquarium.
[ I'm glad you said this. Taking from your own experiences, did you see a difference in the fish size, activity and lifespan between the two systems?] I also pointed out that it is irresponsible to advocate no water change systems for beginners. There are a host of things that you need to know before you can successfully go down this route.
Again I never said that my way was better I say I’ve had equal success. The issue is that you already have predetermined bias for the necessity of water changes because this way has worked for you. It doesn’t mean this is the only method that works. Like I said, I’ve tried both AND I’ve shown you a tank that has had few water changes in 25 years (not my tank), I’ve also given you a store that has sold and bred fish successfully for many years and is quite popular amongst other hobbyists. Why do these points get glossed over repeatedly?
[It doesn't get glossed over, it's been on my mind the entire time I've been responding. In fact, a lot of study was done in keeping marine fish tanks where the algae grown within the system to absorb the nitrates out of the system was fed back to the fish in the tank because it also contained the vitamins and minerals that healthy algae contains making the system entirely self contained. Knowing this, it made me wonder if the same thing was going on with the freshwater systems? Regarding the store that bred and sold fish with no water changes, do you know if he is using or adding anything to the water to add back to it what the fish have absorbed out of it? ]
Of course the hobby stems back way before the 70s. I’m looking at an old aquarium book that that explicitly states that the water should not need changing. My point is that with the advent of larger power filters and tap water conditioners, test kits etc have things truly changed for the better? How many people around the world are not on forums like this because things just work?
[ I have to laugh at your book reference because I also have a book I obtained in the late 1960s that shows a picture of a Marble Veiltail Angelfish with the caption "Not too pretty, it is doubtful that the Marble variety will ever achieve popularity." There are currently 7 different strains of Marble Angelfish recognized by TAS and Marbled was one of my most sold color varieties. LOL They didn't get everything right back then. ]
My only request is that when people say things that they really think carefully about what they are saying is accurate and scientifically proven and IF not just give your experiences and anecdotes and try not to force your beliefs on to others.
I agree nitrates are better at 0ppm. That’s how my tank runs and there’s virtually no nitrate in natural systems.
[There's also no such thing as a no water change system in nature. ] So aiming for 0ppm sounds to me like good practice. But I could just as easily argue that tap water isn’t exactly clean.
[And you would be correct because it isn't. Even rain water in some parts of the world is not safe to drink. Think back to the acid rains found in the midwest of the US. ] What if I made up a statement that flouride in tap water made fish grow bigger? If I could convince enough people….I mean it really has just as much scientific bearing as the whole hormone argument. None at all.