why is it necessary to do weekly 50% water changes? - The Planted Tank Forum
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post #1 of 27 (permalink) Old 08-12-2010, 09:03 AM Thread Starter
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why is it necessary to do weekly 50% water changes?

sorry if thats a silly q to you guys..im new to this. i keep reading on many many posts about doing a 50% weekly water changes if i have high light,fertz,co2 etc... and even to do it with a low light setup i think.

my understanding was that the fish and fertz and co2 provide the nutrients which the plants take up..in the process they take up ammonia and nitrites which r toxic to fish at small levels but the plants use them for nutrients.

my question is... why do i have to do weekly water changes instead of doing a water change only when my nitrAte levels start getting too high?
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post #2 of 27 (permalink) Old 08-12-2010, 09:28 AM
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Originally Posted by nicks7.1985 View Post
sorry if thats a silly q to you guys..im new to this. i keep reading on many many posts about doing a 50% weekly water changes if i have high light,fertz,co2 etc... and even to do it with a low light setup i think.

my understanding was that the fish and fertz and co2 provide the nutrients which the plants take up..in the process they take up ammonia and nitrites which r toxic to fish at small levels but the plants use them for nutrients.

my question is... why do i have to do weekly water changes instead of doing a water change only when my nitrAte levels start getting too high?
For a planted tank 25% every 1 -2 weeks is sufficient - solely depending on stocking levels of course.

50% water changes is for discus really, and you never use so much fert that the fish suffer.
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post #3 of 27 (permalink) Old 08-12-2010, 09:30 AM
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The reason for wc's is to re-set the nutrients being added to your tank. In different situations, wc's are not a necessity. If you are doing a Walsted style NPT, a wc happens bi-annually if that. With a high light e.i. style tank, nutrients are dosed with excess. I forget the actual numbers but with ei based fert doses and maximum plant uptake, the max of a certain nutrient is 50%(???) of the total dosed for the week. Without a wc and all the excess nutrients, an imbalance may occur which in turns may lead to algae. You do a wc to get all your nutrients back to a known value, which will at or near 0.
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post #4 of 27 (permalink) Old 08-12-2010, 09:37 AM Thread Starter
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ahh that makes sense nocturnal kid...well im planning to start off with low light but depending on how long its taking the plants to grow i may switch to high.
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post #5 of 27 (permalink) Old 08-12-2010, 09:56 AM
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ahh that makes sense nocturnal kid...well im planning to start off with low light but depending on how long its taking the plants to grow i may switch to high.

In high light tanks, wc are done for acheiving a balance between co2, lights, ferts. If one is out of whack, algae rears it's ugly head. Wc are also done for the fauna in your tank. You can have 60ppm of nitrates with no algae but I dont think your fish will be too happy.

I have 2 low tech tanks with no co2. One gets a 25% wc every week because of shrimps, and another get top offs and a wc maybe every year or so. Plants grow great and no algae. The shrimp tank gets ferts every time I do wc and the other tank gets its ferts from fish poo.
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post #6 of 27 (permalink) Old 08-12-2010, 10:01 AM
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Actually the w/c is for the build up of unwanted chemicals that are harmful to the fauna such as ammonia, nitrate, etc. Its not to reset the nutrients. I first belived what you did nocturnal kid by in that doing a 50% w/c it would reset the nutirent levels when dosing methods such as EI. But after talking and reading alot with the guys who created it I actually found out its for the fish. Think about it when you dose methods like EI you allready putting excess nutrients into the water, the whole reason of EI and other methods are to put more nutrients in than needed so 'reseting' them as such would be counter-productive.

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post #7 of 27 (permalink) Old 08-12-2010, 12:56 PM
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Originally Posted by Swan900 View Post
Actually the w/c is for the build up of unwanted chemicals that are harmful to the fauna such as ammonia, nitrate, etc. Its not to reset the nutrients. I first belived what you did nocturnal kid by in that doing a 50% w/c it would reset the nutirent levels when dosing methods such as EI. But after talking and reading alot with the guys who created it I actually found out its for the fish. Think about it when you dose methods like EI you allready putting excess nutrients into the water, the whole reason of EI and other methods are to put more nutrients in than needed so 'reseting' them as such would be counter-productive.

I have to disagree. Based on what I know about EI, we dose in excess of what we need ( limitless nutrients ) to rule that out as a source of growth concerns. Then, we do a 50% water change to reset the tank. If you dont do the water change and just continue to dose EI there is a good chance that you will build up excess nutrients and cause yourself heartache in many ways.

In an understocked planted tank with low lights and no EI the water can go a long time without being changed. The plants will use the fish waste as food and the bacteria in the tank will take care of the rest.

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post #8 of 27 (permalink) Old 08-12-2010, 01:38 PM
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I have to agree with Nocturnalkid and Shane3fan, the 50% water change is to reset the nutrient levels in the aquarium, and also to remove the extra build up of nitrites. Shane3fan covered the whole thing beautifly.
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post #9 of 27 (permalink) Old 08-12-2010, 01:41 PM
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the 50% WC is NOT for the fish. For the fish no water changes are needed in heavily planted tanks. The plants are all the nitrate control you'll ever need.

It's to reset the ferts each week so that you don't have to test NPK levels all the time to know (read: estimate) what is in the tank.

Head over to tom's site and read up. In other words, get it from the horse's mouth. barrreport.com


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post #10 of 27 (permalink) Old 08-12-2010, 02:02 PM
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Actually, in a heavily planted tank, you still need to do water changes. It's to replace certain minerals and trace elements in the water. But a large plant mass does relieve the need for frequent water changes.

And don' worry nicks, the only stupid questions are the ones that go unasked.

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post #11 of 27 (permalink) Old 08-12-2010, 02:06 PM
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^these elements will be replaced by topoff water if you're using tap.

my low tech tank used to get a change every year just to be sure if that counts.


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post #12 of 27 (permalink) Old 08-12-2010, 02:11 PM
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Originally Posted by jargonchipmunk View Post
the 50% WC is NOT for the fish. For the fish no water changes are needed in heavily planted tanks. The plants are all the nitrate control you'll ever need.
I would be careful as to what you say.
IMO, MAYBE you can get away with "no water changes are needed in a heavily planted tank", if you MAYBE, I doubt... had a limited stock of fish.
People are going to take your words literally, stock up their tank with
what they think is "heavily" planted, and think they are set.
An ESTABLISHED planted tank that has been running for at least 12 -
18 months, using their plants as a "biological" filter takes years to do.
Anyhow, IMO it is ridiculous not to do any water changes in a tank with something living. Most people in this hobby aren't going to be able to do that cept for maybe Tom Barr and a few others.
There is no rule as to how many water changes you should do in your tank, planted of otherwise. But, I would say, most would agree that there needs
to be SOME KIND OF WATER CHANGE, at least to get the bacteria and
anything else out of the bottom of the substrate that would build up after a years time and not break down.
To answer the original Q to the poster... you don't wait until your ammonia and nitrates are high before you do a water change. You will stress your fish out, and take the chance of disease and death.
You want to keep your water parameters stable, which IMO will be virtually impossible with no water changes cept for someone besides an "expert", who has unlimited resources with money, time and lots experience.
Sometimes I wonder if people who are "into" the planted tanks care more about their planted tank, then the living, breathing fish in it.

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post #13 of 27 (permalink) Old 08-12-2010, 02:21 PM
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Quote:
Originally Posted by sean117Ply View Post
For a planted tank 25% every 1 -2 weeks is sufficient - solely depending on stocking levels of course.

50% water changes is for discus really, and you never use so much fert that the fish suffer.
This is a pretty inaccurate statement.'nough said
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post #14 of 27 (permalink) Old 08-12-2010, 02:23 PM
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I'm sure the fish appreciate fresh water the same way we appreciate fresh air, and it surely isn't going to hurt them. Plants are nice, but the fish are the creatures that really need to be considered.
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post #15 of 27 (permalink) Old 08-12-2010, 02:27 PM
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I'm sure the fish appreciate fresh water the same way we appreciate fresh air, and it surely isn't going to hurt them. Plants are nice, but the fish are the creatures that really need to be considered.
Yep. I agree.

In my book, the best thing you can do for your aquarium is a water change. I try and do a weekly 50% water change or a bi-weekly 30%.

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