Quote:
Originally Posted by Dino
I just do not follow the logic.
It would seem to me, that any improvement of the water conditions, should be beneficial to your fish.
Taking away harmful chemicals should always help your fish.
If temperature and pH are close in the new water, I do not see that a single 50% or a series of smaller changes, would make a difference.
But I have no experince to back that up, as my tanks do not go a month without a change.
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The theory (I have no recent experience in the matter, so this is based on what I've read in books, and seems to be backed up by the experiences of past aquarists, before people knew what a partial water change was) is that a fish's body acclimates to a particular quality of water. So far, so good. We know this to be true. If it weren't, a goldfish wouldn't even be able to
survive in a little bowl.
So then, when a fish's body becomes acclimated to the much higher level of nitrates (and all of the changes that might cause, such as a lower pH), and then the water is quickly changed out, the fish's body goes through a minor shock. Usually wouldn't be problematic, except the fish's body was already weakened by being in too much waste.
This does make a certain amount of sense, figuring that osmosis has evened things out so the cells are pretty close to the water around them, then you suddenly change the water quality (even for the better), forcing the cells to go through a pretty rapid osmotic process to even things out again.
In the past (that time before partial water changes), fish would often go through shock when the owners broke the tank down and did monthly or bi-monthly maintenance, changing all or nearly all of the water in the tank. Sometimes the fish would die within hours of the change (not to mention the ones who died in a couple of days due to ammonia build-up. I'm guilty of that one).
Of course, this is a more extreme situation than 3 weeks, but it's closer than I'd like to worry about.
Actually, now that I think about it, I have killed one fish by doing this, but not in any of my tanks. When I took over caring for the tank at my brother's day program, I did a 30% water change, and one of the fish was dead by the next morning. Of course, this was a case of the water not being changed for months and months because the employees didn't know they were supposed to do it.
Honestly, I think it's a matter of determining the lesser of two evils. In this case, you're probably right that it wouldn't hurt the fish.
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I think that should be illegal! They're living creatures, not disposable art! I wonder how one would go about getting that categorized as "animal cruelty"?
Doesn't seem right.