Taking the time to streamline water changes is well worth the effort. I have a long hose and use a pump to empty, tap water to fill. And the laundry room sink is about 35' away. Got it pretty much down to a science now.I do 50% now. More would be quite a bit of work, especially as I'm still hauling five gallon buckets thru two rooms to do it!
If your fish are used to large changes than it really doesn't matter as much if the parameters are off a bit.You can do large water changes without any negative effect as long as water chemistry/parameters stay stable throughout the change. Of course you want to mind not stressing the fish out so much just from the act of the water change (you and the siphon's presence and lowering water levels).
So take note of water parameters currently/going out and water parameters going in, they should be very close to cause minimal stress load on the fish. Note if water changes are done infrequently or whatever reasons cause water parameters to change quickly so that new fresh water may have a significantly different set of parameters. The more change/difference, the more load/work/stress that puts on the fish to adapt to.
I got a 20 gallon brute trashcan(made from plastic) with a pump attached to a white freshwater drinking hose. I fill up the aquarium, treat the water with prime and with a digital thermometer ensure the temperature is the same.When I had bettas in bowls I did 80-90% wc every week. But now that I have bigger tanks that are much more stable, that would seem overkill to me, unless I had done replanting and stirred up a crapload of mulm. I do 50% now. More would be quite a bit of work, especially as I'm still hauling five gallon buckets thru two rooms to do it!
Yeah, Chloramines is ammonia and Chlorine(both deadly combination to fish). The tap water conditioner can neutralize the chlorine however the ammonia is left over.I've noticed with my tanks that pH goes up as the water matures. I start out low, about 6.2, and by the end of the week it is at 7.4 sometimes. I don't have substrate or filters, just floating plants and stem plants held down with one or two metamorphic quartzite type rock commonly found here in Virginia. If that can happen without much influence, then substrate and filters, etc., can have an effect on chemistry even more so. If you have high pH, and drop it quickly, it could be detrimental to the fish. So depending on your setup and fish and starting water chemistry, you can afford to do 90% or just 50% weekly without damage. I mostly just add water that evaporates and do a 25% water change monthly since I have floating plants do the filtering, and my pH, etc., doesn't swing so wide that my fish are hurt. Oh, and my water doesn't contain Chloramines. That makes a BIG difference from what I understand.
It depends again on how much your aquarium water changes over the week. It does change, the question is how much and in what way. But theoretically, yes, if your tap water matches your aquarium water after a week, you can change it all! In my experience, that has never been the case. For example: I use my well water for 8 months out of the year (warm weather hoses to house) which is at the very low 5.8 pH often. My tanks may be at a constant 7.4 pH. So, smaller water change is necessary not to shock fish. I use my House water 4 months out of the year, County Water, at a pH of 7.2 or 7.4 on average, so I can easily do a 100% water change if I've had enough coffee that morning, without worry.So if the tap water has.
1. Same temperature
2. Same PH
3. water condition to handle the chloramines and resulting ammonia.
4. Same water hardness.
Then you could do larger water changes?
If there is a storm water issue, my County water can really swing as well. In the mid summer doldrums, the water reservoir can get nasty, and chloramines are possibly added if high bacterial count cannot be handled by chlorine. I've smelled the chlorine from the tap in those times. Luckily, I use the well in summer.Personally my tap water parameter swing wildly one week to the next. I have seen 30 TDS one week, 200 TDS the next. So a big 90% water change would do more harm than good. So the most I would do is 50%. And I would refill super slowly over 30mins to give livestock time to adjust.