# How much PWC is recommended ?



## MarcGh (Oct 11, 2011)

Hello,
Until recently I had a 28 Gallon tank and I did the PWC as follows:
20% every Wednesday + 40% every Saturday or Sunday.

I have now a 100 Gallon tank stocked as in my signature and would like to now what is recommended for frequency and volume for the PWC.

I did not perform any PWC for 1 full week and my water readings (Nutrafin drop test) are as follows:
Last week wednesday: PH 7.6 - Nitrit 0.0 - Ammonia 0.0
Today (Wednesday): PH 7.2 - Nitrit 0.1 - Ammonia 0.0

I am a bit worried about the drop in the PH value. Is this normal?
I can't test the Nitrates as the drops in the bottle are finished. I will have a new Nitrate test kit in about 10 days.

How should I go about tne PWC? 
Btw, If I listen to my kids (8yo and 11yo) we should do it every day or possible 2 times or more a day........

Thanks for your advise,
Marc


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## jrman83 (Jul 9, 2010)

When did you take the ph reading? A tank with plants can have a slightly higher ph at the end of the lighting period when the plants have been using up the CO2 in the water. Not sure how many of the plants you have in your tank. I notice very little difference in mine and they are heavily planted....before I added CO2 anyway.

Do you have a kh test kit? Have you ever tested the ph of your tap and also set aside some tap water and tested 24hrs later? This is good data to know. If you have some crushed coral, you can add some (very little) to help hold your ph steady but it would be good to know kh and the ph of your tap now and 24hrs later.

I change 50% of my water every week.


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## Kev1jm2 (Oct 18, 2011)

I still don't understand the point of weekly partial water changes in a heavily planted and filtered tank. But, to each his own.


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## jrman83 (Jul 9, 2010)

Kev1jm2 said:


> I still don't understand the point of weekly partial water changes in a heavily planted and filtered tank. But, to each his own.


In a high tech tank with fairly high intesity lighting, CO2, daily dozed ferts it is actually a necessity to reset nutrient quantities.

Aside from that, it is just good practice I did before I went planted. Keeps your water safe and keeps the accumulation of dissolved solids that cause things like constant creeping (higher) ph, to a safer level.


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## majerah1 (Oct 29, 2010)

I do 50% on mine as well,because I dose ferts and CO2,and feel its for the health of the tank.


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## Kev1jm2 (Oct 18, 2011)

jrman83 said:


> In a high tech tank with fairly high intesity lighting, CO2, daily dozed ferts it is actually a necessity to reset nutrient quantities.
> 
> Aside from that, it is just good practice I did before I went planted. Keeps your water safe and keeps the accumulation of dissolved solids that cause things like constant creeping (higher) ph, to a safer level.


In a high tech tank I definitely agree with you. But in a low tech tank, i think the stability of limited water changes has great benefits.


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## jrman83 (Jul 9, 2010)

As does regular water changes. Any benefit of no water changes, can be met with just as many as doing regular water changes. I will never believe that tanks with little to no water changes will ever be healthier than one that gets. There are arguments on both sides of the fence.


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## Kev1jm2 (Oct 18, 2011)

Jr, you may be correct. Just presenting the other side


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## beaslbob (May 29, 2009)

In a planted tank low.no ammonia and nitrites are normal. But you can get an initial nitrate spike.

pH should be higher but sounds about right.

to me the best way to maintain a tank is to balance it out with live plants and to use peat moss in the substrate. The peat moss IME tends to keep hardness in line.


I do that and then do no water changes just replace evaporative losses. And have had thriving tanks for up to 9 years with descendants from the original cycle fish.

my .02


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## jrman83 (Jul 9, 2010)

beaslbob said:


> pH should be higher but sounds about right.


Why should ph be higher?


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## BBradbury (Apr 22, 2011)

Hello marc...

You seem to have a lot of concern about your tank's water chemistry. I don't have the years of experience that some of the other folks on this forum do but, if you start and follow an aggressive water change routine of replacing a minimum of half the tank water every week, you don't have to worry about water conditions.

Large and frequent water changes keep the chemistry of the water in your tank stable and stability is the most important to your fish and plants.

If you do your water changes religiously, there's no reason to test your water parameters, you know they're "spot on".

IMO, tank keepers waste too much time messing around with water chemistry. By flushing a lot of clean, treated water thorough your tank, you guarantee a stable enviroment for your fish and plants.

My advice is, do your water changes and the fish and plants will be fine.

B


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## beaslbob (May 29, 2009)

jrman83 said:


> Why should ph be higher?


Part of the nitrogen cycle is an increase in carbon dioxide which lowers PH.

In the case in one week pH went from 7.6 to 7.2 and nitrItes from 0 to .1.

So that is just a classic cycles.

With a planted tank pH should rise (just before lights out) because the plants are sucking out the cardon dioxide. 

I also get a 1 day bump up of nitrItes to .1 then it drops down to 0 the next day.

So if pH has fallen and nitrItes bumped up perhaps one should stop adding food until both recover. At least that's what I do and get recovery in 2 days max.

My pH in my planted tanks is also much higher (8.4-8.8 (purple) on the api high range test kit.) But the 7.6 could be the max reading on the api pH (non high range) test kit. So possibily the pH was initially much higher therefore the pH drop is more pronounced.

So bottom line the pH drop indicates increased carbon dioxide.

Still just my .02


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## jrman83 (Jul 9, 2010)

beaslbob said:


> Part of the nitrogen cycle is an increase in carbon dioxide which lowers PH.
> 
> In the case in one week pH went from 7.6 to 7.2 and nitrItes from 0 to .1.
> 
> ...


That is essentially what I posted at the top of the thread. I never saw a drop of more than .2-.3 at the end of my lighting cycles before I started adding in CO2. I completely understand how CO2 affects a tanks ph. Mine swing a full point from pressurized CO2.


I just didn't understand your comment about how the ph should be higher.


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## beaslbob (May 29, 2009)

jrman83 said:


> ...
> 
> I just didn't understand your comment about how the ph should be higher.


Just my experience with a tank full of anacharis.

his and your mileage (and pH ) may vary. *old dude

worth at most .02


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## fishguy2727 (Sep 5, 2011)

There are many bad things that build up in ANY tank. These include growth inhibiting hormones and dissolved organic compounds. Although a planted tank can handle fewer water changes than the equivalent unplanted tank, they still need them, and will do better with them. 

In an unplanted tank all the bad things tend to correlate with nitrate, but since planted tanks remove nitrate, but not the other bad things, you can get false results that look better than they really are.


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## beaslbob (May 29, 2009)

fishguy2727 said:


> There are many bad things that build up in ANY tank. These include growth inhibiting hormones and dissolved organic compounds. Although a planted tank can handle fewer water changes than the equivalent unplanted tank, they still need them, and will do better with them.
> 
> In an unplanted tank all the bad things tend to correlate with nitrate, but since planted tanks remove nitrate, but not the other bad things, you can get false results that look better than they really are.


I disagree with this and hopefully you know with respect.

Plants are one of the most effective water filters so much so that industrial waste sites are cleaned up by enviromental engineers with both live and dried plants. 

By contrast water changes at levels and intervals convienent to the aquariumist (10% weekly 30% monthly etc) will limit but not prevent changes to the environment. 
Which is why unplanted tank have 100ppm of high nitrates plus algae problems and so on.

Additionally relying on water changes also relys on the condition of the replacement water making the tank suspectable to seasonal changes and the like.

By contrast plants with no water changes will reach a healthy, stable, and balanced state where both the fish and plants thrive. 

All us lowly humans can do is screw up the environment.*old dude

But still just my .02


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## fishguy2727 (Sep 5, 2011)

Plants help, but they are not 100%. Yes, they are a great form of natural filtration, but they don't remove all the bad things that build up. They do not remove growth inhibiting hormones. 

Yes, inadequate water changes will cause problems. If you have a nitrate concentration of 100ppm you are not doing enough water changes. Equating the problems with inadequate water changes to water changes in general is errored. A tank should get enough water changes to keep the nitrate concentration under 20ppm. My usual recommendation is weekly water changes, this frequency prevents the tap water from being too different than the tank water and causing certain problems. The amount will vary from tank to tank, minimum 25%, more if needed to keep the nitrate under control. 

I agree that a planted tank may not need as large of a water change as an unplanted tank, but to consider water changes in a planted or unplanted tank as a negative thing is simply wrong IME.


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## jrman83 (Jul 9, 2010)

beaslbob said:


> I disagree with this and hopefully you know with respect.
> 
> Plants are one of the most effective water filters so much so that industrial waste sites are cleaned up by enviromental engineers with both live and dried plants.
> 
> ...


Although I don't agree with everything you said, I can agree with most. But, I also think that plants are not the answer to all there is to a tank that doesn't get water changes. It may be an environment suitable for fish and plants, but I can argue the same for water changes. Water changes are not unhealthy. Yes, you may not have to deal with as much with topoffs if the water source is slightly screwed. However, those things the aquarists learns to work around and only the inexperienced will have problems getting it right in his/her tank. 

As good as plants are at filtering, explain how you always state that plants drive up ph? Plants do not do this! It YOUR tanks this happens! I'm not talking about the daily up and down use of CO2 in the water by the plants. I believe it is from never getting the water refreshed and the TDS in the water just builds and builds, which will drive up ph over time. The plants can do a lot, but in the case of year after year without a water change, they are limited. Very few people that I have come in contact with either in person or the thousands on the internet forums deal with a ph that is as high as you have stated you have (8.5+), not to mention the incredibly high gh you've mentioned (35+). I can keep my gh at the same level it was 18 months ago (10) and I am on well water. Do frequent water changes and watch the level come back down to where it started straight from your tap. I will gladly let you borrow my TDS meter to test your water. Just my .02


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## fishguy2727 (Sep 5, 2011)

Plants can use KH as a carbon source, which will actually drive the pH down over time. I have seen this happen in well planted tanks with no water changes. Eventually the pH was too low to register on test kits. The TDS may go up, but there has to be some KH there to hold pH up.


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## beaslbob (May 29, 2009)

jccaclimber said:


> Bob, do you have a filter on your salt tanks?


Actually I did use a wet/dry on my 55g which was just a wastebasket full of crushed oyster shells. in a 29 gallon I had a sump with chaeto only.

So on one tank yes on another no.

I did use the diy 2 part to maintain calcium,alk,mag on both tanks.

In both tanks nitrates and phosphates (salifert kit) were unmeasureable.

my .02


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## beaslbob (May 29, 2009)

jrman83 said:


> Although I don't agree with everything you said, I can agree with most. But, I also think that plants are not the answer to all there is to a tank that doesn't get water changes. It may be an environment suitable for fish and plants, but I can argue the same for water changes. Water changes are not unhealthy. Yes, you may not have to deal with as much with topoffs if the water source is slightly screwed. However, those things the aquarists learns to work around and only the inexperienced will have problems getting it right in his/her tank.
> 
> As good as plants are at filtering, explain how you always state that plants drive up ph? Plants do not do this! It YOUR tanks this happens! I'm not talking about the daily up and down use of CO2 in the water by the plants. I believe it is from never getting the water refreshed and the TDS in the water just builds and builds, which will drive up ph over time. The plants can do a lot, but in the case of year after year without a water change, they are limited. Very few people that I have come in contact with either in person or the thousands on the internet forums deal with a ph that is as high as you have stated you have (8.5+), not to mention the incredibly high gh you've mentioned (35+). I can keep my gh at the same level it was 18 months ago (10) and I am on well water. Do frequent water changes and watch the level come back down to where it started straight from your tap. I will gladly let you borrow my TDS meter to test your water. Just my .02


With peat moss in the substrate my kH stays at 4 degrees, gh stays at 9 degrees for over two years.

pH rises as plants change the tank into a net daily consumer of carbon dioxide and producer of oxygen. and perhaps helped by my no circulation as well. In a 55g marine tank with plenty of circulation, ph rose from 7.5 to 8 in a day after adding marco algaes and then to 8.4-8.8 (api high range test kit) in a week and stayed there for years with no buffers added. With low kh the nightly ph did drop to 7.9 or so. After starting the diy 2 part and maintaining kH with baking soda, the nightly drop seemed less.


Removing carbon dioxide causes pH to rise with no change in kH. Plus the plants consuming nitrates returns carbonate ions used up by the aerobic reduction of ammonia and nitrItes.

So in my experience even with peat moss in the substrate the plant action results in high pH.

but still just my .02


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## beaslbob (May 29, 2009)

FWIW here is article on pH, carbon dioxide, and kh (alk) for reef tanks.

The same principles apply to planted FW tank as well.

Low pH: Causes and Cures by Randy Holmes-Farley - Reefkeeping.com

my .02


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## jrman83 (Jul 9, 2010)

beaslbob said:


> With peat moss in the substrate my kH stays at 4 degrees, gh stays at 9 degrees for over two years.
> 
> pH rises as plants change the tank into a net daily consumer of carbon dioxide and producer of oxygen. and perhaps helped by my no circulation as well. In a 55g marine tank with plenty of circulation, ph rose from 7.5 to 8 in a day after adding marco algaes and then to 8.4-8.8 (api high range test kit) in a week and stayed there for years with no buffers added. With low kh the nightly ph did drop to 7.9 or so. After starting the diy 2 part and maintaining kH with baking soda, the nightly drop seemed less.
> 
> ...


Again, not arguing what plants do to a waters ph when it is consuming the CO2. That is just part of plants being in there, whether the tank turns in a net consumer or not. If the plant is living it is using CO2, bottom line. This is not what I am talking about.

Plants do not make your ph continue to rise beyond their use of the CO2. However, this is what you have said you've experienced in your tanks. In other words, if your tap ph is 7.0, you will not see an eventual rise to 8+ just because you have plants. In fact, you'll see a dip to 6.7 or so and then back to 7.0 by time the lights come back on. If an eventual and continual rise occurred, then hi-tech tanks with ph controllers would need to pump more and more CO2 to reach the set ph in the controller and eventually reach a point that it would start affecting the fish. If you have seen a continuous rise, then it is likely it is all the organics in your tanks that have not been consumed by the plants.

CO2 controllers kick on when a level is attained (the high end setting) at the sensor and turns off when the ph has been lowered to the setting.

I won't argue what you've seen in saltwater tanks, but the info doesn't always cross and I don't know jack about the subject.


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## beaslbob (May 29, 2009)

jrman83 said:


> Again, not arguing what plants do to a waters ph when it is consuming the CO2. That is just part of plants being in there, whether the tank turns in a net consumer or not. If the plant is living it is using CO2, bottom line. This is not what I am talking about.
> 
> Plants do not make your ph continue to rise beyond their use of the CO2. However, this is what you have said you've experienced in your tanks. In other words, if your tap ph is 7.0, you will not see an eventual rise to 8+ just because you have plants. In fact, you'll see a dip to 6.7 or so and then back to 7.0 by time the lights come back on. If an eventual and continual rise occurred, then hi-tech tanks with ph controllers would need to pump more and more CO2 to reach the set ph in the controller and eventually reach a point that it would start affecting the fish. If you have seen a continuous rise, then it is likely it is all the organics in your tanks that have not been consumed by the plants.
> 
> ...


I guess we just have different experiences. *old dude

my .02


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## MarcGh (Oct 11, 2011)

BBradbury said:


> Hello marc...
> 
> You seem to have a lot of concern about your tank's water chemistry. I don't have the years of experience that some of the other folks on this forum do but, if you start and follow an aggressive water change routine of replacing a minimum of half the tank water every week, you don't have to worry about water conditions.
> 
> ...


After reading a lot about PWC on this forum and other literature I decided to go for the regular/weekly one.
Think I just want to keep it on the safe side of the hobby...

So today I changed 100 Liters water equal to +/- 25% content. Same time I cleaned the gravel and glass, re-arranged my few plants.

Kids,myself end the :animated_fish_swimm are happy with the result.

Thanks to all .
Marc


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## jrman83 (Jul 9, 2010)

beaslbob said:


> I guess we just have different experiences. *old dude
> 
> my .02


Sort of what I was getting at. Your experiences is strictly based off of your practices, IMO. A tank with normal water changes will have the same ph just before the lighting cycle, day in and day out. Otherwise, things like ph controllers would not even work.


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## beaslbob (May 29, 2009)

jrman83 said:


> Sort of what I was getting at. Your experiences is strictly based off of your practices, IMO. A tank with normal water changes will have the same ph just before the lighting cycle, day in and day out. Otherwise, things like ph controllers would not even work.


absolutely.

Our only disagreement is the resulting pH level.

Gee I though pH controllers were used (among other things) to control the amount of carbon dioxide being added. *old dude

my .02


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## beaslbob (May 29, 2009)

jccaclimber said:


> pH controllers are used to control CO2 added, but if plants caused a long term change in pH as you claim, the controller would have to be constantly adjusted, which they don't.


As I understand it pH controlers turn on carbon dioxide at some level and off at some other level. So all they would do is just cycle more often and add more carbon dioxide with plants then without.

No adjustment needed.

my .02


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## beaslbob (May 29, 2009)

jccaclimber said:


> Not quite. The pH drop is based on CO2 added. If the natural CO2 level kept being raising, and the set point stayed the same, more CO2 would be added as time went on. At some point you would gas the fish.


So?

For instance assume you have my mythical (to you) system where pH just before lights out was say... 8.5. With higher alk dropping to say 8.4 at night with less alk dropping to 7.9 at night. (note actual measured values on 55g marine setup).

So now we add co2. That say turn on at 7.9 and off at say 7.5 So during the day the co2 turns on as the plant life sucks out the co2 and the ph rises above 7.9. pH continues to fall as more co2 is being added then the plants can consume until the tank reaches 7.5. At that point the co2 cuts off. As the plants suck out the co2 pH rises so the co2 kicks in at 7.9 again.

If the tank never gets above the 7.9 the co2 never kicks in. the faster the plants (and circulation) remove the co2 the quicker the co2 cycles dumping more into the tank. 

If the fish can live at a pH of 7.5 they will do fine.

so it just seems to me that with plants you dump in more co2 then without plants. 

Of course I believe based on my experience that if fish can survive a pH of 7.5 (or 7 or 6.5) they can thrive even better at a ph of 8.4-8.8. After all the only difference is lower carbon dioxide in the water. Which should mean they can literally breath a whole lot easier.

All I know is I have pH values of 8.4-8.8 (api high range test kit) which drops down at night at lower KH values and remains much more constant at night with higher kH values.

And even fish (like neons, hatchetfish) reported to "need" soft lower pH water (6-7) live and thrive for years and years at that high ph.


my .02


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## jrman83 (Jul 9, 2010)

CO2 controllers are used for two things...to attain a certain ph (for things like species specific requirements ie. Discus) and to attain a certain level ppm for CO2.

If the natural ph in the tank continues to rise on its own as you have stated you see in your tanks, when using a contoller your adjustments for on/off of the CO2 would need to be continuously adjusted. It would come on sooner, kick on/off more, and stay on longer when it was on. Or on the other side may cause it to stay on less time and end up wrecking your plants depending on your light level. You would contantly be fighting your water to get it to stabalize and more than likely end up gassing your fish or coming close at some point. Most guys using controllers for plant use take note of the ph when the right level of CO2 is attained (right color reached on their drop checker) and use that setting as their lower end point to turn off the CO2.


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## jrman83 (Jul 9, 2010)

Plus, a ph that continuously rises for any reason is not a stable tank...sort of quoting Walstad there. If plants caused ph levels to eventually peak in the 8+ range and that is where it stopped and steadied out, you wouldn't see very many Discus owners keeping heavily planted tanks, which coincidentally is the only way I have seen them. They are arguably the most ph stringent fish out there. You also wouldn't be able to keep many species of freshwater shrimp in it either. I have kept Cardinals in 8.2 (my tap) with no problems...I know they can adjust. I have also been reading some stuff that is sort of making believe it is due to the large amount of peat used in your substrate setup, although I could be wrong. Walstad and Kasselman both advise against it. Although I know it is used in higher end substrates, just not in high abundance however, as it is mixed in with everything.


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