Water cange percentages and Frequency - The Planted Tank Forum
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post #1 of 37 (permalink) Old 10-24-2016, 01:13 PM Thread Starter
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Water cange percentages and Frequency

I have a +- 10 gallon planted tank in my office at work, high pressure CO2 and am dosing EI. Because of the way I'm situated (right across the hall from the men's room) it's much easier for me to do a small (10%-15%) daily water change than to do a weekly 50% change. I have a little Tupperware container that holds about a half gallon of water, for small water changes I scoop out a couple of containers full of water, dump them in the john and re-plenish, it takes me about 5 minutes. For a large water change I've got to drag in the big 5 gallon bucket, it's more hassle and also a bit more disruptive. If I do a small water change each morning before dosing my ferts, will it work out the same as doing a weekly 50% water change? Thanks.
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post #2 of 37 (permalink) Old 10-24-2016, 03:43 PM
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I have a +- 10 gallon planted tank in my office at work, high pressure CO2 and am dosing EI. Because of the way I'm situated (right across the hall from the men's room) it's much easier for me to do a small (10%-15%) daily water change than to do a weekly 50% change. I have a little Tupperware container that holds about a half gallon of water, for small water changes I scoop out a couple of containers full of water, dump them in the john and re-plenish, it takes me about 5 minutes. For a large water change I've got to drag in the big 5 gallon bucket, it's more hassle and also a bit more disruptive. If I do a small water change each morning before dosing my ferts, will it work out the same as doing a weekly 50% water change? Thanks.
your water change % and frequency will depend on your tank. If your tank has a good ratio of plants and the water is balanced, you may only need to change it twice a year. If you have less plants and your water gets funky quickly, you will have to change it more often. 50% weekly is about as much as you would need to change it. It helps put good stuff in your tank and take out bad stuff in your tank. look at your plants as if they are your doctor report. you are the PHD MD DR. tank master. use your understanding to determine how to prescribe the water change.

i would say a 50% water change every month would be a better place to start. changing the water too often will let the algae thrive off the sudden changes while your plants are always struggling to catch up and adapt to the new water parameters.
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post #3 of 37 (permalink) Old 10-24-2016, 04:44 PM Thread Starter
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I was asking more specifically because I am dosing EI ferts. With EI the reccommendation is a weekly 50% water change to prevent an excess buildup of nutrients because EI is designed to provide essentially an over abundance of nutrients so that they don't become the limiting factor in plant growth. My quesion is will it work out the same with EI doing the smaller daily water changes vs the large weekly change.
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post #4 of 37 (permalink) Old 10-24-2016, 05:23 PM
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Originally Posted by redchaser View Post
I was asking more specifically because I am dosing EI ferts. With EI the reccommendation is a weekly 50% water change to prevent an excess buildup of nutrients because EI is designed to provide essentially an over abundance of nutrients so that they don't become the limiting factor in plant growth. My quesion is will it work out the same with EI doing the smaller daily water changes vs the large weekly change.
yes you can do small water changes vs big water changes. itll remove bad stuff and put back in good stuff. I would say 50% weekly is too much. 50% monthly is more like it.
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post #5 of 37 (permalink) Old 10-24-2016, 05:56 PM
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Originally Posted by redchaser View Post
I was asking more specifically because I am dosing EI ferts. With EI the reccommendation is a weekly 50% water change to prevent an excess buildup of nutrients because EI is designed to provide essentially an over abundance of nutrients so that they don't become the limiting factor in plant growth. My quesion is will it work out the same with EI doing the smaller daily water changes vs the large weekly change.

NO! Typically you can do small water changes. But you really cant do that if you're dosing ferts via the EI method. The whole point of the EI method is you dose fertilizers daily to reach an oerabundance of ferts by the end of the week (which you said yourself). Then you need to "reset" with a big water change but only at the end of the week after you've added in all the ferts. Doing daily water changes would completely defeat this idea as you would be removing the ferts you just added and would never get the over abundance of nutrients.


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yes you can do small water changes vs big water changes. itll remove bad stuff and put back in good stuff. I would say 50% weekly is too much. 50% monthly is more like it.
In certain situations you can do small water changes effectively. But you need to understand the situation before making that decision. Since the OP is dosing ferts via the EI method 50 % weekly water changes is exactly whats needed (as he laid out above by saying the recommendation is to provide an overabundance of nutrients and then weekly 50% WC to prevent the buildup of excess nutrients). Doing small daily changes would be a waste and doing monthly 50% changes would likely be deadly to any livestock in the tank.

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post #6 of 37 (permalink) Old 10-24-2016, 06:05 PM Thread Starter
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IKSdrinker, thanks, I appreciate the response that actually cosidered what was asked. We all may have a preferred method or theory, but it's not always applicable to every situation.
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post #7 of 37 (permalink) Old 10-24-2016, 06:48 PM
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IKSdrinker, thanks, I appreciate the response that actually cosidered what was asked. We all may have a preferred method or theory, but it's not always applicable to every situation.
@IKSdrinker gave you good advice. Technically if you increasing your dosing somewhat you could probably get a way with more frequent water changes, but weekly is definitely the way to go with your tank. Also daily water changes will get old really fast and most don't keep up with it. If you could use a python at office that would make the water change a 5 minute process.
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post #8 of 37 (permalink) Old 10-24-2016, 06:56 PM
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Changing 50% of the water once a week, the most nutrients can possibly build up is 2x whatever is dosed between water changes. This is assuming zero plant uptake.

Changing 30% of the water, the most that can build up is 3x the amounts dosed between water changes.

Changing 10% of the water every day, would essentially be like doing no water changes, and dosing 10% less than you're actually doing. There'd be an eventual ceiling where the concentration no longer increased, but it would be high.

So as far as regulating the nutrient build up, this is not a good plan in conjunction with EI. There would be a never ending rise in nutrients.

Small frequent water changes do have their advantage. A constant supply of fresh new water is good for the whole system. Plants and fish love it. Algae hates it.

I remember an old thread on Barr Report talking about if you do a 10% water change every day you'll never have bba. Dont think enough people tried it out to really put the theory to the test, but it had some merit imo. Digressing a little...

If 10-15% daily water change is the only option, then you should find a dosing routine that pretty much targets what the plants actually use, or just a tad above.

How much the plants use will depend on your individual set up. How many plants and what kind, how much light intensity - that sort of thing.

You'll have to play it by ear for a while to find the sweet spot. if I had to guess, something like 1/4 EI 2x week might be a good place to start.

Then keep an eye on nitrate and/or phosphate levels as a proxy for what the tank is actually using. I say these two because they are easy to test for.

Test maybe once a week for a few weeks. If the levels continue to climb, reduce the dosing. If the levels get too low, increase the dosing.

Somebody else may have a better solution for you. But that's the only way I can think of to run a "high tech" tank with that kind of WC routine.

You may want to look into pps-pro dosing. It does sort of the same thing, but there are still water changes involved at certain times. I believe when TDS reaches a certain point, which has never made logical sense to me, but you may find some of the theory useful to apply in your case.


TL;DR - Find a way to do weekly 50% water changes


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post #9 of 37 (permalink) Old 10-24-2016, 07:02 PM Thread Starter
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Changing 50% of the water once a week, the most nutrients can possibly build up is 2x whatever is dosed between water changes. This is assuming zero plant uptake.

Changing 30% of the water, the most that can build up is 3x the amounts dosed between water changes.

Changing 10% of the water every day, would essentially be like doing no water changes, and dosing 10% less than you're actually doing.

So as far as regulating the nutrient build up, this is not a good plan in conjunction with EI. There would be a never ending rise in nutrients.

Small frequent water changes do have their advantage. A constant supply of fresh new water is good for the whole system. Plants and fish love it. Algae hates it.

I remember an old thread on Barr Report talking about if you do a 10% water change every day you'll never have bba. Dont think enough people tried it out to really put the theory to the test, but it had some merit imo. Digressing a little...

If 10-15% daily water change is the only option, then you should find a dosing routine that pretty much targets what the plants use, or just a tad above.

How much the plants use will depend on your individual set up. How many plants and what kind, how much light intensity - that sort of thing.

You'll have to play it by ear for a while to find the sweet spot. if I had to guess, something like 1/4 EI 2x week might be a good place to start.

Then keep an eye on nitrate and/or phosphate levels as a proxy for what the tank is actually using. I say these two because they are easy to test for.

Test maybe once a week for a few weeks. If the levels continue to climb, reduce the dosing. If the levels get too low, increase the dosing.

Somebody else may have a better solution for you. But that's the only way I can think of to run a "high tech" tank with that kind of WC routine.

Also you may want to look into pps-pro dosing. It does sort of the same thing, but there are still water changes involved at certain times. I believe when TDS reaches a certain point, which has never made logical sense to me, but you may find some of the theory useful to apply in your case.


TL;DR - Find a way to do weekly 50% water changes

Thanks,

I can do the 50% once weekly, it's just a real PITA. I'll stick with it
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post #10 of 37 (permalink) Old 10-24-2016, 07:29 PM
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Thanks,

I can do the 50% once weekly, it's just a real PITA. I'll stick with it
doing a 50% weekly change is back breaking and indeed PITA. I think its better to have a balanced tank and change the water every 2-6 months to save the hassle.
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post #11 of 37 (permalink) Old 10-24-2016, 07:43 PM
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i would say a 50% water change every month would be a better place to start. changing the water too often will let the algae thrive off the sudden changes while your plants are always struggling to catch up and adapt to the new water parameters.

3 times you've recommended that the OP not do regular water changes. The first post clearly says he's using the EI method. Regular water changes (typically weekly) are a big part of the EI method. EI dosing with 50% water change a month is a recipe for disaster.

Plants don't have to struggle to catch up, or adapt to proper conditions and parameters.
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post #12 of 37 (permalink) Old 10-24-2016, 07:46 PM
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My favorite way to keep my tanks is to just dose twice immediately after a large water change every week. Macros immediately after the change and then micros in the morning the next day. That's it for the week. I dose far less than EI levels (about 1/3 - 1/2 the amount) because I really don't think you need that much unless you are running on full blast.

Larger water changes are preferred by a lot of people who keep higher tech tanks and have to dose all the time. Like burr said the larger changes help to 'reset' your fert levels so you can't have a crazy buildup of nutrients over time if you are dosing more than you should. You can dose more liberally and still avoid having high levels because they don't have much time to build up before you cut everything in half (50% change). A leaner, more regimented approach is more appropriate for smaller water changes which is a PITA so many people don't do it that way.

If you take the super-low-tech road you can create a very balanced tank that does not need frequent water changes like IntotheWRX said. In a higher tech setup with higher light, CO2, ferts, etc this is not feasible IMO. I'm personally a strong proponent of doing water changes at least once a month regardless though.

I feel you with not wanting a sheetrock bucket for water changes at work lol. I used to have a nano tank at my desk and considered a 10g before setting it up. The main reason I didn't was the hassle of changing that much water in the office lol.

I do 50% changes on my 10g hospital tank sitting on the floor at home. I use a larger-sized tupperware container and a sheetrock bucket. Only tanks like 15 minutes to scoop 5g out into the sheetrock bucket, refill in the tub, and scoop the water back in. I would recommend this as a good option for you if you decide to do the 50% per week.

Having a high tech 10g tank with CO2 at work is awesome though! Good for you


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post #13 of 37 (permalink) Old 10-24-2016, 08:02 PM
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doing a 50% weekly change is back breaking and indeed PITA. I think its better to have a balanced tank and change the water every 2-6 months to save the hassle.
OP has a 10 gallon tank.....really not all too demanding to remove 5 gallons and add in another 5 gallons once every 7 days. You're 100% correct about it being better to achieve balance. But you are again not looking at the OP's situation where he is choosing to dose ferts via the EI method. You cant arbitrarily guess that a water change once ever 2-6 months (quite a big variance there) will actually help you achieve any sort of balance. Then you also need to know what exactly you're trying to balance?.....if its a balance of free time vs time maintaining your fish tank(s) then sure once every few months should work very well!

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post #14 of 37 (permalink) Old 10-24-2016, 10:26 PM
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There's no glory in balancing a tank. It usually means you are putting in plants you might not want, reducing your light, reducing your fish load, etc. You have to find a narrow range that would work. When you change water on a regular basis you increase the range a tank can be run whether it's with less plants, more light, more stock. Gives you more freedom for the tank to look the way you want.

@IntotheWRX

I've seen you give your no water change advise in thread after thread regardless of whether the OP was using EI, Aquasoil, high-light, etc. I've also seen you flame people and leave perverted posts in various threads (including one of mine) which was removed by the moderators.

Your tank journal is a poster thread for why water changes are good. You started a tank with Aquasoil threw fish in within a week and most jumped out to escape the toxic conditions. You then started getting BBA and figured you would raise the co2 to I think 10 BPS in which you gased a bunch of fish. For some reason every time a fish died you had the urge to make a joke about it. Your now (last post are saw) down to like 4 hrs of light and dosing excel constantly to fight the BBA. That is not a balanced tank, not even close. So your doing all this and going around stating water changes are a waste of water, yeah right.
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post #15 of 37 (permalink) Old 10-25-2016, 02:11 AM
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Common sense tells it's better to do small changes more often. It's better to clean toilet a little every day instead of waiting whole week for large cleaning, correct?

Let's try to prove it. Here is math.
b - is the amount of daily changes (10%, for example) 0<b<1
a - coefficient of daily water "freshness", i.e. a=1 - water stays fresh all the time, a=0.2 - means if 100% fresh water is added, then it'll be only 20% fresh next day. This coefficient is measure of kaka buildup, etc,
0<a<1

One can write geometrical progression to calculate "freshness" of water ever day. Kinda simple (9 grade?) but I will omit it (drop me a line if you really want to know). Assuming we start from "dirty" water (freshness=0). Then, after the Nth change:

F=b* (1 - (1-b)^N*a^N) /( 1- (1-b)*a)

If we do changes every day, then after long run freshness:

F=b/(1-(1-b)/a)

10% daily changes (b=0.1) and 90% freshness coeff (a=0.9) in a long run, water will be 0.52 fresh constantly.

If we replace 50% once a week, then (a=0.9 as above) water freshness goes from 0.5 (after changing) to 0.27 before next change. Which is significantly worse than 0.52.

You can play yourself with numbers in Excel


This game of numbers is simply to illustrate small frequent changes is better:

1) Environment is cleaner.
2) Environment is more stable. For example less swing in pH, etc. Of course, sometimes it's needed, for example, to induce fish spawning
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