how bad is this???

[petspoiler]

And if this guy felt a need to do a 100% water change its possible its because his water quality was bad. All I'm saying is from what I've read it encourages that 100% water change as long as dechlorinated can do no harm at all. That's how it will look to newbies which is a dangerous thing on both sides

ANY THREAD discussing water maintenance should be read in full, and comments be taken in context. Every contributor should not have to (and will not) go back over the whole thread and reiterate every single point made, & every situational example for every person who comes along & starts jumping all around.
For instance, discus breeders do not have neglected conditions. Neither do other breeders who maintain fry tanks with the practice of constant inflow of fresh water, so that frequent feedings will not build up waste at all.

 

[petspoiler]

...................... I have never seen fish go into any kind of "shock" in my house after doing a 75 - 90% water change as long as the temps matched. In fact, that large of a water change usually triggers spawning.

^Exactly.

 

[David R]

Wow that sounds SOOO Familiar... And now it is good advice!!!! ROTFLMAO....

Except that I would suggest using dechlorinator, as despite being on the older end of the average age here I have read things and learned that the science behind the "gassing off" method of dechlorinating water is wrong.

BUT-- if your tank is reasonably well maintained in the first place your nitrates won't be so high as to shock your fish with a water change of whatever volume.

The question is why, if your nitrates aren't sky high, would you want to change more than 50% of the water at once?

I'm not sure I buy into the theory of "nitrate shock" and as suggested if you've let them get that high then big water changes aren't the answer, more frequent [smaller] changes are. I know big water changes have their place with heavily stocked grow out tanks, but I cannot for the life of me see the sense in changing more than half of the water in one hit with your average properly filtered well maintained home aquarium. You are literally flushing money down the drain with the extra heating and water costs.

 

[neutrino]

The question is why, if your nitrates aren't sky high, would you want to change more than 50% of the water at once?

That's a good question. The answer is that nitrates are not the only reason to change water. There are other organic compounds to keep low and there are minerals to replace as they are used by plants, algae, fish metabolism, etc. Also, as noted by others above, some fish respond to such water changes by taking it as a cue to spawn, whether this is due to difference in water quality, minerals, or simply a temperature change that mimics changes in their natural environment.

But, again, how much water you need to change to maintain water quality and how much you can change safely can be two different things. And then it comes down to personal philosophy, opinion, or preference. Everyone has their own approach. Personally, what I do varies from one tank to another, based on a variety of things, including having developed an eye for water quality after many years, at least in my own tanks. I have one tank that I typically change 30% each week and nitrates are low, reading about 5. I have another tank I typically change @70% each week, more to do with inhabitants and effect on behavior/spawning than a requirement for water quality. I have certain times of year in my area where my well water doesn't look so good and I'll change water less frequently and less volume.

My whole thing with water changes is and always has been there's no one-size-fits-all formula, couldn't tell you how many times I've posted this over the years. With all the variations of setup, stock, filtration and equipment, feeding, local water quality, cost of water, etc. imo it's best to figure out what works best for you, not to rely on what someone else does in their tank with its own peculiarities.

 

[Jc1119]

Except that I would suggest using dechlorinator, as despite being on the older end of the average age here I have read things and learned that the science behind the "gassing off" method of dechlorinating water is wrong.



The question is why, if your nitrates aren't sky high, would you want to change more than 50% of the water at once?

I'm not sure I buy into the theory of "nitrate shock" and as suggested if you've let them get that high then big water changes aren't the answer, more frequent [smaller] changes are. I know big water changes have their place with heavily stocked grow out tanks, but I cannot for the life of me see the sense in changing more than half of the water in one hit with your average properly filtered well maintained home aquarium. You are literally flushing money down the drain with the extra heating and water costs.

My nitrates are never high, but I've found larger changes really do help with growth, especially fry which in my house are fed 4-5 times a day. They also induce spawning if needed in my experience.

I think it also depends on your situation.....my fry and growout tanks are in my garage in Florida. Ambient temps are very high. I might run heaters on those tanks for a week or two in January. The drip system actually helps keep my tank temps much lower without using a chiller and it keeps the water chemistry very stable since its a continual, slow process. And for those on well water, its much cheaper to change more water than to go crazy with filtration.

But if I lived somewhere where heaters were necessary, I can certainly see how it would be a waste.


Sent from my iPhone using MonsterAquariaNetwork app

 

[David R]

Drip systems are a whole different ball game! Changing large quantities with a drip system is far better than doing it all at once as you get consistency. If you've got cheap/free tap water that suits your fish then a continuous flow of water through the tank is the way to go. In an ideal world we would just have a constant flow of clean water running though our tanks instead of filtration, but when the incoming water doesn't match what the fish need (temperature, conductivity, hardness etc) we need to look at how much water needs to be changed to keep the fish healthy, rather than just going overkill.

That's a good question. The answer is that nitrates are not the only reason to change water. There are other organic compounds to keep low and there are minerals to replace as they are used by plants, algae, fish metabolism, etc. Also, as noted by others above, some fish respond to such water changes by taking it as a cue to spawn, whether this is due to difference in water quality, minerals, or simply a temperature change that mimics changes in their natural environment.

But, again, how much water you need to change to maintain water quality and how much you can change safely can be two different things.
My whole thing with water changes is and always has been there's no one-size-fits-all formula, couldn't tell you how many times I've posted this over the years.

You're dead right, there is no one size fits all answer. I'm well aware that there are more to water changes than nitrates, otherwise I wouldn't be changing any water on my tank at all! I'm not sure how many of those unknowns are more critical than nitrate though, I think in most cases if you stop changing water then high nitrates will be the first thing to start causing problems for your fish. I guess it really comes down to your tap water and how it suits your fish, and how much trouble you're willing to go to to match your aquarium water. And how tough your fish are!

So, obviously there is no one-size-fits-all recommendation, but I'm pretty sure everyone would agree that moving your fish to perform a 100% water change is almost never necessary, nor a good idea.