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Why do people say big water changes are bad?


tithra

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Well I am not saying big is wrong, I just find that small frequent changes work for me in my tropical tanks, but then I dont keep waste heavy fish and am a habitual understocker. My planted tanks run with low nits anyway so constantly taking small amounts out seems to work fine for my needs. Like you said - I just stick with whats working :)

Surely also, while removing 10% every other day leaves 90% of the waste in, so doing one huge weekly change leaves 100% in for 6 days in between? I think both methods are a matter of keeping toxins under controlled and harmless levels because if you get into the mathematics of it anything under 100% several times a day is going to be imperfect, and thats beyond most peoples abilities (personally I am out of my house up to 12h a day and dont have a python system because theyre not readily available in the uk - so doing daily 90% wcs like you do on your discus is not optional anyway :[ ).

Plus I know if I did loads of huge water changes all my Bamboo shrimp would starve to death :(

NB - I just did a wc and actually the standard 3 buckets I do is closer to 20% but that doesnt really change my opinion haha :)

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From the point of view of someone who works with people who think that 50% water changes will kill your fish (and gets the evil eye when she mentions 100% water changes...)

My theory is that since most aquarium hobbiests use filter cartridges (and change the cartridges every other week :idont), they don't have a cycle in anything but their gravel. And if they are the good little sheep that we all know they are, they are gonna do a gravel vac when they change water (because..well...how else would they do a water change besides using one of those plastic things the salesman gave them?) If they gravel vac 50% of their tank...they are gonna lose their cycle and, yes, probably kill their fish, and definitely stress them.

I get people all the time at work who tell me about their problems in their tanks and water change schedules...when I suggest large water changes it never fails that I have to explain filters, media, syphoning, substrate, at the same time.

And I invariably tell them that I do 100% water changes at least 6 times a year, if not more. And that's just from moving my fish to school and back and into the pond! That doesn't take into account the 100% water changes I do if I see something amiss...or if I'm bored. :P

And invariably I get shocked responses.

It all comes down to one thing: sheep. Baa.....

Now for marine tanks it's a different story....

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Hmm I think im going to withdraw from this discussion now because I think im going to end up being wrongly associated with people who never change their water or who dont understand tank or cycle mechanics.

(i.e. i am not and have not ever advocated doing one small water change IN PLACE of a large one. I just break my wc up over the week rather than doing it all in one go, for reasons specific to my setup).

I think alot of the feedback has been less discussion and more scoffing/flaming.

Anyway, I just really hope nobody has lumped me in with the "uneducated" " idiots" and "sheep" just because I split my wcs up ;[

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I can only speak for myself, but I don't think anything like that at all Lucerne, I think there is a huge difference between doing a 20% water change every two weeks and a 20% water change every other day! :) And I found your point of view very helpful and appreciate your responses. I'm sorry if I said anything that made you feel uncomfortable or targeted in any way :hug

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This is an interesting topic. Tropical fish hobbyist did an article on it once. They concluded that a bunch of 10% water changes everyday takes something like a month to get all the nasty dirty orignal water out. Every time you do a water change you get only 10% out then you dilute it 10% the next day 10% of the water you are changing was just put in the day before so you are not just changing the dirty wate everytime you do a 10% water change. I guess what i am saying is 10- 10% water changes does not equal a 100% water change.

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Lucerne I would not call you uneducated or stupid you never said big water changes were bad just that you did not do them. Like I said I'm not trying to change anybodys ways and if it works for you dont change doing what you are doing.

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Thanks guys :)

I guess I was just getting paranoid because some people obviously have strong opinions on this, and was the only different one hehe.

Still I think ive said all I know on this really, but its been interesting to hear about what works for different people :]

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I'd like to add that while big water changes are great, it is really crucial that we make sure that the tap water pH is amenable to large changes before making the suggestion to do so. Otherwise, it will be necessary to do the small changes as Lucerne has been doing, which is great at minimizing big changes in the tank as the result of WCs :)

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Lucerne, I actually agree with you. There is a big difference between doing large water changes on messy fish like goldfish in relatively sparse tanks, and water changes in tropical tanks with fish/plants/inverts far less forgiving of water parameter changes.

Guess what would happen if I did a 50% water change on my licorice gouramis? Exactly...

I personally still have to do small but frequent water changes on my goldfish due to pH issues.

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I would never do a 100% water change directly from the tap. I always age my water so that the ph swing happens in the aging barrel and not the tank. Around here the water leaves the tap with a high ph and when you aerate it to get the oxygen/co2 levels balanced the ph will stabilize. So yes it is important to be careful not to swing the parameters when doing large water changes, but if you have the same chemistry entering as leaving you will have no issues. Even with licorice gouramis. O and i have kept them ;)

Edited by Patti
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I have heard this same thing alot among lake tang cichlid keepers as well. Most do not do large water changes. I was always different though even when i was breeding a few lake tangs i always did larger changes of around 50%. I do see both side though I just cant bring myself to not using my siphon alot. I bought the thing i figure i should get as much use out of it as possible. You can take all my filters just dont take my siphon away :wa

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Big 80-90% water changer here, and 100% of the 1"-2" deep gravel gets vac'd at the same time. Straight out of the tap, right into the tank with as big a drop and splash as I can get out of it. No issues.

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I think, based on what I've experienced is that water changes depend on your tank, your fish, and your plants. I have 3 tanks with entirely different needs. One is my over planted correctly stocked guppies/mollies tank, I only need to do a 50% every month. My lightly planted Mollie tank needs one every 2 weeks. My temp Goldie tank with no plants needs one every 3 days How do I tell? I watch the fish closely every day, when the toxins are starting to be unsuitable they will start to become slightly less energetic. The moment I notice this behavior I immediately change water, they perk all the way back up.

I find a once a week regiment is best for those who don't have the time to inspect and watch their fish closely enough. But if you look close enough they'll tell you when it's time :)

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I think, based on what I've experienced is that water changes depend on your tank, your fish, and your plants. I have 3 tanks with entirely different needs. One is my over planted correctly stocked guppies/mollies tank, I only need to do a 50% every month. My lightly planted Mollie tank needs one every 2 weeks. My temp Goldie tank with no plants needs one every 3 days How do I tell? I watch the fish closely every day, when the toxins are starting to be unsuitable they will start to become slightly less energetic. The moment I notice this behavior I immediately change water, they perk all the way back up.

I find a once a week regiment is best for those who don't have the time to inspect and watch their fish closely enough. But if you look close enough they'll tell you when it's time :)

I'm not sure that waiting until your goldfish show signs of stress or slowing down before you do a water change is a very good idea. Chronic stress in such a manner may lower their immunity to infection overall. I would check your tank to see the pattern of how long BEFORE these signs appear and do water changes before that. :)

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I think, based on what I've experienced is that water changes depend on your tank, your fish, and your plants. I have 3 tanks with entirely different needs. One is my over planted correctly stocked guppies/mollies tank, I only need to do a 50% every month. My lightly planted Mollie tank needs one every 2 weeks. My temp Goldie tank with no plants needs one every 3 days How do I tell? I watch the fish closely every day, when the toxins are starting to be unsuitable they will start to become slightly less energetic. The moment I notice this behavior I immediately change water, they perk all the way back up.

I find a once a week regiment is best for those who don't have the time to inspect and watch their fish closely enough. But if you look close enough they'll tell you when it's time

I'm not sure that waiting until your goldfish show signs of stress or slowing down before you do a water change is a very good idea. Chronic stress in such a manner may lower their immunity to infection overall. I would check your tank to see the pattern of how long BEFORE these signs appear and do water changes before that.

Lol I shoulda been a little more specific, I do use their reactions to tell me how often and plan before hand. very rarely do I need to adjust my actions to make sure they're happy. What I wanted to say was. "Watch your fish for awhile and take action against stress to figure the pattern of needed water changes, but if you don't have time for close analysis just do a precautionary once a week." :)

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Ok so after reading this thread. I don't know if I should change or stick to what I've been doing.

I currently do 2 x 40% water changes a week. I test the nitrate once a week before the second water change and it never goes above 10ppm.

I have 3 goldfish in a 40 gal tank.

The reason I do 2 40% is to vacuum more regularly and because my tank ph is 7.8 and tap ph is 7.4. And I try to match temp by finger method. So I thought cause my param matchig isn't as accurate I thought smaller 40% changes would stress them less. Also I have ammonia out of tap of 0.5. So I also thought a larger wc will actually be introducing more ammonia into the tank even though I do use prime. It would take time for filter to consume it.

My question is should I do larger wc less frequently or stick to what I'm doing based on my reasonings? And how come my nitrate builds up so slowly compared to u guys? Should I be feeding more? Oh I also have 3 large Anubis plants attached to driftwood maybe that's y nitrate is less

Thanks again

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That pH difference is quite acceptable. Do your large pH to your heart's content :)

That pH difference is quite acceptable. Do your large pH to your heart's content :)

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Yes, as Alex said, a difference of .5 or less in Ph is acceptable :) You will be fine doing big water changes.

I'm sure the 3 anubias do a little for your nitrates, but probably nothing dramatic. Significant nitrate reduction requires heavier planting than that I believe.

The .5 ammonia will be detoxified by the Prime and therefore not harmful to your fish :)

How big are your 3 goldfish? I have two large (6 and 7 inches) goldies in a 40 gallon and am on a pretty heavy feeding schedule and I never really get nitrate readings (granted the longest I typically go between water changes is 5 days, usually it's more like every 2-3 days).

If you are concerned about your feeding schedule you might start a thread in the food section to get input from others :)

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What about the temp difference and the reduced gravel vac? Or That doesn't matter too much?

My fish are lot smaller than yours. I have 1 that is 5cm and 2 that are 3cm long body only.

I'll post my food schedule in the feeding part as u suggested

Thx :)

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What about the temp difference and the reduced gravel vac? Or That doesn't matter too much?

My fish are lot smaller than yours. I have 1 that is 5cm and 2 that are 3cm long body only.

I'll post my food schedule in the feeding part as u suggested

Thx :)

you should definitely match temp as close as you can when you do the water change :) I use my finger to do this as well. I find I am usually within 1-2 degrees.

Your fish are pretty small yet, that is probably why you are not getting nitrate readings :)

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