When doing a large water change you can add prime right to the tank (your filter is turned off when doing large 90% water changes) and add you new fresh water to the system. The chemicals are in no way going to harm your filters BB.
I think if throw your tank into a mini cycle its because the water is not being treated properly. this means even a smaller water change can have negative impact on your aquarium life.
Anyhow, I have and know many who have done large water changes daily while growing out adult fish and fry with no issues at all. In fact I have grow out fish faster and healthier using this method.
Some how my point seems to have been missed. Without scientific proof your statement is anecdotal evidence yet you accused moe214 of spreading misinformation. In of itself stating personal experiences as irrefutable scientific fact is more a kin to misinformation then someone stating their opinion.
As far as experiences go I myself can site others who are of similar belief and have had experiences counter to yours yet unlike you I don't use that to dismiss anyone else's opinion that is counter to mine publicly. I myself had a bad incident where I did a significant wate change because I had been neglectful earlier in the week. How ever unknown to me line work was being done and despite using water conditioners and testing the tap water prior to initiating the change I almost lost all my fish. The fish didn't react right away(survival imperative makes them act healthy even if they feel like death till they can't fake the funk anymore). How ever shortly after the change was completed I noticed distress. Rapid gill movements and general disinterest in my presence. Then I guess the weaker more fragile species started gasping at the surface. Lucky for me the workers decided to inform us after the work was completed that the water should be safe again. So I quickly did another significant change and luckily only lost one fish. Yet even when addressing this situation about large water changes despite my personal experiences I stated that this is my opinion based on what I consider logical deduction. All in the attempt to not do what you did which was pass off anecdotal evidence as fact. Why because without knowing the scientific reasons behind my experiences I can't say anything definitively and shouldn't therefore present it as fact.
There are plenty of people who claim to have seen bigfoot, does that equal irrefutable scientific evidence that bigfoot must exist? That's the biggest issue with misinformation, anecdotal evidence should never be presented as fact. I met a elderly woman with a Pacu that had to be over 20 inches in a 55 gallon who only topped off her water that evaporated rather then actually do a change. Does that mean I should follow her lead or treat her experiences as a definitive fact that can be applied to all fish and aquarium situations? Moe214 never stated anything as definitive as you did. Yet you chose to attack his opinion by calling it misinformation with nothing other then personal experiences of you and others you knows as the basis to present your statement as fact. I simply hoped you'd see my point and just show your fellow members posts a little more respect.
As for the actual point of whether large water changes might cause issues. I'll start with the fact that water conditioners state that for best results the water should be pre-treated and if not the dose used should be upped for the entire aquarium volume. That in of itself shows that those who created the product believe there is an inherent risk in not pre-treating water. Since their statements are almost guaranteed backed by scientific data, the very same data they used to develop said product and legally market it, it's very likely there is indeed a risk associated with water treated after introduction to the tank and logically any risk of course would be heightened by the higher concentration of chemicals and contaminants in a large water change versus a smaller one.
Water conditioners usually address specifically chlorine, chloramine, and ammonia. Detoxifies nitrite and nitrate and helps protect and stimulate growth of the slime coat. Not PH jumps created by outgassing or many of the other chemicals found in tap water. What about the other chemicals commonly found in tap water? Here's just a few of those chemicals :
Liquified chlorine, fluorosilicic acid, aluminum sulphate, calcium hydroxide, sodium silicofluoride.
Now here's just a few contaminants:
Chlorine, Fluorine compounds, Trihalomethanes, Salts of: arsenic, aluminium, copper, lead,mercury, cadmium, barium as well as Hormones, Nitrates and Pesticides. Things that can negatively affect people never mind fish or bacteria.
I'm sorry but I believe subjecting the fish and bacteria to higher concentrations of these things has a risk? Can you name a conditioner or group of aquarium conditioners that targets all the chemicals, contaminants and out gassing I've listed?
Now I'm not saying your statement isn't true for you or your friends but to make a broad statement and present it as fact without accounting for everyone's in every area and with every kind of tap water could actually cause harm. What about areas that use well water or areas that are really far from the reservoir and the pipes are showing their age or where the water has been contaminated by line work or a natural disaster such as contamination due to unusual run off that hadn't been detected yet? The fact is in such cases and in many where water supplies aren't as stable as others there's a real possibility of causing a major problem by doing a large water change which would subject the tank inhabitants to higher concentrations of contaminants then a smaller water change.
