Simple Math Table: Large Daily Water Changes = Consistently Good Water

[zergling]

The veterans here in Simply Discus have decades of first-hand experience in breeding and raising discus. All of them consistently preach large daily water changes - daily 50% is (in my opinion, at least) the standard in water change volume and frequency.

However, we consistently have new hobbyists questioning the volume and the frequency of water changes. For most of these hobbyists, "decades of experience show this is the best way" is not a good enough reason.

For these hobbyists, I offer you a simple math table below to support why Discus veterans preach water changes. This shows that mathematically, large Daily Water changes will bring consistently good water levels.

ASSUMPTION # 1: The new water you put in the tank does NOT add pollutants. If the water you use has nitrates or other pollutants to start with, then this table does NOT apply to you.
ASSUMPTION # 2: Nitrates and other DOC's / pollutants need to be kept as low as possible to allow Discus to grow to their genetic potential. If this theory is (somehow?) disproved, then this table is no longer worthwhile.

The table below shows simple math forecasting the build-up of Nitrates* over the span of 9 weeks. It assumes that the Nitrate levels in the tank raises an additional 5ppm per day.
*I had nitrates in mind when I created the table, but the math can apply to other pollutants
http://i.imgur.com/BimaOX5.png

Clearly, daily 50% water changes will never allow Nitrate levels to go above 5ppm (or whatever Nitrate level the tank produces on a daily basis). Daily 40% water changes does not allow Nitrate levels to go above 7.5ppm, or 1.5 times what the tank produces on a daily basis. Anything less than these two will show Nitrate level build-up to 10ppm or higher.
- If your tank produces considerably less than 5ppm of Nitrates daily, then obviously you can get away with a little less water changes.
- If your tank produces considerably more than 5ppm of Nitrates daily, then you most likely will need more than Daily 50% water changes.

About Planted Tanks:
- It is a known fact that live plants consume Nitrates.
- It is also a known fact that live plants have their own needs - Carbon, Nitrogen, Phosphorous, Potassium, trace elements.
- When live plants do not get ALL their needs, they do not grow well or perish - this is when ugly Algae will take over.
Plants should only be considered as a supplement to water changes. Now, if you have DECADES of experience with live aquatic plants and raising discus, then please chime in because all hobbyists would love to learn from your knowledge and experiences.

Hey zergling, your table is useless because I read about a guy who bred and raised discus in tanks with minimal water changes!
That's great! If you know anyone that has raised Discus from 2-3" (or smaller/younger!) to 6" or bigger, please encourage that person to take a picture of the discus on a measuring stick, and share it here!

Hope this helps!



"TOO LONG; DIDN'T READ" VERSION:
Assuming your tank produces about 5ppm of Nitrates from wastes every day, you have three options for water changes to keep Nitrates below 10ppm:
1) Daily Water Change - 40-100% (Offers the least amount of fluctuation of Nitrate levels thanks to high frequency WC)
2) Every 2 Days Water Change - 60-100% (Happy medium between #1 and #3)
3) Every 3 Days Water Change - 90-100% (Some fluctuation of Nitrate levels, barely above 10ppm)

[Solid]

This is a fantastic table illustrating the benefits of large water changes. It is also important to note that nitrates are a good example to use here, but are not the only chemical we are trying to control. Many people might measure there Nitrates and say hey they are around 10 ppm no need to worry, but not realize that other dissolved organic matter or bacteria is building up to toxic levels. Good thing large water changes also help keep these other un-testable elements under control as well.

I am somewhat familiar with the math, but perhaps you could add larger than 50% water changes. I have started doing 80%-90% every other day rather than 50% everyday, because it's my understanding that larger water changes are more efficient.

[zergling]

I am somewhat familiar with the math, but perhaps you could add larger than 50% water changes. I have started doing 80%-90% every other day rather than 50% everyday, because it's my understanding that larger water changes are more efficient.

That's a good idea. Ceteris paribus, More time between WC's = More fluctuation with Nitrate levels. However, I'm curious how the volume of the WC helps with that.

[Second Hand Pat]

You can use the WC percentage in this article from the SimplyDiscus library http://www.simplydiscus.com/library/discus_husbandry/discus_basics/wc_formula.shtml

[zergling]

You can use the WC percentage in this article from the SimplyDiscus library http://www.simplydiscus.com/library/discus_husbandry/discus_basics/wc_formula.shtml
Thanks Pat, that is actually the foundation of the formula I used on the tables. I've done 2 things from that foundation:
1) Assigned an arbitrary value (5ppm) for a day's worth of waste / daily increment.
2) Expanded into visual tables, showing different frequencies and volumes.

Solid's suggestion led me to make multiple tables to show the differences between Volume and Frequency.

Short Version:
Assuming the tank produces a daily increment of 5ppm for a day's worth of wastes, you have three options for water changes to keep Nitrates below 10ppm:
1) Daily Water Change - 40-100% (Offers the least amount of fluctuation of Nitrate levels thanks to high frequency WC)
2) Every 2 Days Water Change - 60-100% (Happy medium between #1 and #3)
3) Every 3 Days Water Change - 90-100% (Some fluctuation of Nitrate levels, barely above 10ppm)

The next few 5 posts will show 5 tables, showing different water change frequencies

[zergling]

Daily Water Changes
http://i.imgur.com/TTf7bn5.png

[zergling]

Water Change Every 2 Days
http://i.imgur.com/VumeKAY.png

[zergling]

Water Change Every 3 Days
http://i.imgur.com/rWav0o2.png

[zergling]

Water Change Every 4 Days
http://i.imgur.com/rhbjdIG.png

[zergling]

Weekly Water Change
http://i.imgur.com/PwDoL0s.png

[Larry Bugg]

The veterans here in Simply Discus have decades of first-hand experience in breeding and raising discus. All of them consistently preach large daily water changes - daily 50% is (in my opinion, at least) the standard in water change volume and frequency.


I have a question for you. Is the above statement referring to juvie discus or all discus? As written, I believe the statement is incorrect. I don't believe all the veterans consistently preach large (50% or more) daily water changes for all discus. I believe the statement is correct for growing out juvies but I don't believe it is correct for adults.

[zergling]

I have a question for you. Is the above statement referring to juvie discus or all discus? As written, I believe the statement is incorrect. I don't believe all the veterans consistently preach large (50% or more) daily water changes for all discus. I believe the statement is correct for growing out juvies but I don't believe it is correct for adults.

Hi Larry,

1) Notice that I said "breeding and raising discus" in the first sentence right before it? I was referring specifically to raising young discus to adult hood (as apparently adults don't need that much water change volume and frequency).
2) I should have been more specific in the second sentence - not all readers assume that context typically remains constant unless otherwise specified.
3) I wanted to edit the original post to this, but the forum no longer allows me to do so.

The veterans here in Simply Discus have decades of first-hand experience in breeding and raising discus. All of them consistently preach large daily water changes when raising young discus to adulthood - daily 50% water changes typically being the standard in water change volume and frequency.

Thanks for chiming in!

PS - Regardless of context, the simple math shows that if the tank produces 5ppm of Nitrates per day, there are only a few water change volume and frequency options available to keep Nitrate levels below 10ppm. If a veteran indicates that discus (young or adult, doesn't matter) are OK with Nitrate levels higher than that (say, 15ppm? 20ppm? More?), then the conclusions will be adjusted (though the math stays the same).

[Larry Bugg]

Thanks for the clarification. I thought you were probably referring to growing out discus but it simply didn't read that way to me and I imagine others would read it the same way I did. I don't want to detract from your chart which is the real point of this thread but there is another current thread that makes a general statement about Simply members adamantly prescribing large frequent water changes for discus and also not specifying young discus. My worry is that people read these statements and use them out of context when giving advice about water changes.

[LizStreithorst]

I don't think it's right for adults either. With fry and juvies the more fresh clean water the better. Growing kids can't get enough new water. They eat tons and poop tons. Adults eat less because they are past the critical fast growth stage.

[zergling]

Thanks for the clarification. I thought you were probably referring to growing out discus but it simply didn't read that way to me and I imagine others would read it the same way I did. I don't want to detract from your chart which is the real point of this thread but there is another current thread that makes a general statement about Simply members adamantly prescribing large frequent water changes for discus and also not specifying young discus. My worry is that people read these statements and use them out of context when giving advice about water changes.

Thank you for bringing it up! Context definitely need to be repeatedly declared with qualifiers, otherwise it's pretty easy for readers to miss the point and not bother with the reject the rest of the post.

[zergling]

I don't think it's right for adults either. With fry and juvies the more fresh clean water the better. Growing kids can't get enough new water. They eat tons and poop tons. Adults eat less because they are past the critical fast growth stage.

Hi Mama Bear,

I addressed that above, see post #12. It was too late to edit my first post when I realized I have to clarify (repeatedly) the context.

Additionally, the math doesn't care if your tank is full of fry or juvies or 8"+ adults. The math only cares about how much waste your tank produces daily: If it produces 5ppm of Nitrates per day, you only have a few options of water change frequency and volume to stay below a target of 10ppm of Nitrates. If your waste production is lower or your target level is higher, then you have more options for water change frequency and volume.

Thanks for chiming in!

[zergling]

I expanded the math calculations further, this time using the same formula to calculate through the range of 1 to 10ppm of daily Nitrate production.

If you know how much Nitrates your tank produces daily, you can see below your options regarding frequency and volume of water changes, to stay below 10ppm Nitrate levels.
If you do NOT know how much Nitrates your tank produces daily, then you should acquire a test kit to measure it, or play it safe and perform daily 50% water changes.
Daily Nitrate Production: 1ppm
Target level: Less than 10ppm
- 10%-100% Daily
- 20%-100% Every 2 days.
- 30%-100% Every 3 days.
- 40%-100% Every 4 days.
- 50%-100% Every 5 days. (40% Every 5 days can "peak" to 11.47ppm)
- 60%-100% Every 6 days. (50% Every 6 days can "peak" to 10.98ppm)
- 70%-100% Weekly. (60% Weekly can "peak" to 10.66ppm)

Daily Nitrate Production: 2ppm
Target level: Less than 10ppm
- 20%-100% Daily
- 40%-100% Every 2 days. (30% Every 2 days can "peak" to 11.33ppm)
- 50%-100% Every 3 days.
- 70%-100% Every 4 days. (60% Every 4 days can "peak" to 11.33ppm)
- 90%-100% Every 5 days. (80% Every 5 days can "peak" to 10.50ppm)
- 100% Every 6 days. (90% Every 6 days can "peak" to 11.33ppm)

Daily Nitrate Production: 3ppm
Target level: Less than 10ppm
- 30%-100% Daily (20% Daily can "peak" to 11.99ppm)
- 50%-100% Every 2 days. (40% Every 2 days can "peak" to 11.99ppm)
- 70%-100% Every 3 days. (60% Every 3 days can "peak" to 11.99ppm)
- 100% Every 4 days. (90% Every 4 days can "peak" to 10.33ppm; 80% Every 4 days can "peak" to 12ppm)
- 100% Every 5 days can "peak" to 12ppm.

Daily Nitrate Production: 4ppm
Target level: Less than 10ppm
- 30%-100% Daily
- 60%-100% Every 2 days. (50% Every 2 days can "peak" to 12ppm)
- 90%-100% Every 3 days. (80% Every 3 days can "peak" to 11ppm)
- 100% Every 4 days can "peak" to 12ppm.

Daily Nitrate Production: 5ppm
Target level: Less than 10ppm
- 40%-100% Daily (30% Daily can peak to 11.66ppm)
- 70%-100% Every 2 days. (60% Every 2 days can "peak" to 11.67ppm)
- 100% Every 3 days. (90% Every 3 days can "peak" to 11.67ppm)

Daily Nitrate Production: 6ppm
Target level: Less than 10ppm
- 40%-100% Daily
- 80%-100% Every 2 days. (70% Every 2 days can "peak" to 11.14ppm)
- 100% Every 3 days can "peak" to 12ppm.

Daily Nitrate Production: 7ppm
Target level: Less than 10ppm
- 50%-100% Daily (40% Daily can "peak" to 10.5ppm)
- 90%-100% Every 2 days. (80% Every 2 days can "peak" to 10.5ppm)
- 100% Every 3 days can "peak" to 12ppm.

Daily Nitrate Production: 8ppm
Target level: Less than 10ppm
- 50%-100% Daily (40% Daily can "peak" to 12ppm)
- 90%-100% Every 2 days.

Daily Nitrate Production: 9ppm
Target level: Less than 10ppm
- 50%-100% Daily
- 100% Every 2 days. (90% Every 2 days can "peak" to 11ppm)

Daily Nitrate Production: 10ppm
Target level: Less than 10ppm
- 60%-100% Daily (50% Daily can "peak" to 10ppm)
- 100% Every 2 days.

I can post the tables behind the summaries above, just let me know if anyone wants to see them.

Note: With the added range of daily Nitrate production above, the numbers are now independent of Discus size or age. The math doesn't care if it is young or juvie or jumbo platter discus. The math only cares about 2 variables: The daily Nitrate production, and the Desired/Target level of Nitrates.

[zergling]

But wait, there's more!!

Don't worry, just one last table to summarize all the calculations I've made:

http://i.imgur.com/pNbbNpy.png

If you know how much Nitrates your tank produces daily, you can see above what your options are regarding frequency and volume of water changes, to stay below 10ppm Nitrate levels.
If you do NOT know how much Nitrates your tank produces daily, then you should acquire a test kit to measure it, or play it safe and perform daily 50% water changes.

I basically took the water change formula in the SimplyDiscus library and expanded it through a range of Daily Nitrate Production, WC Frequency, and WC Volume. 10 spreadsheets with 7 tabs each, summarized in the table above.

Again, I'd like to reiterate and make sure it's clear:
- The math doesn't care if it is young or juvie or jumbo platter discus. Hell, the math doesn't even care if it discus or a horde of guppies in the tank.
- The math only cares about 2 things: How much Nitrates does your tank produce daily? It assumes that the Desired/Target level of Nitrates is 10ppm or lower.

[Solid]

This is some great info thanks Nathan!

[cellingson]

And this is assuming that the reason we do water changes is to bring down nitrate levels. Much discussions have been had that the importance of a water change goes beyond nitrates.
That being said. Well done. I will copy, print, cut out, and paste that last table to my aquarium log book. Very nice!

[zergling]

This is some great info thanks Nathan!
Thanks Matt!


And this is assuming that the reason we do water changes is to bring down nitrate levels. Much discussions have been had that the importance of a water change goes beyond nitrates.
That being said. Well done. I will copy, print, cut out, and paste that last table to my aquarium log book. Very nice!
Thanks! I specifically called out Nitrates because it can be tested for, and also applies to other freshwater fish tanks.

The math can also apply to any other pollutants or DOC's - that's IF we can measure the rate they are produced and have a target level we want to achieve.

The math doesn't apply to nitrates in saltwater tanks because they have denitrification. The math also doesn't directly apply to other water parameters that doesn't build up constantly / linearly - pH, GH, kH, dissolved O2 and CO2 levels, etc.

[Blademan]

Hi I have a 80gallon show tank, plus 30 gallon sump with ten, 4.5 to 5 inch discus, after three days the nitrate level will rise to between 10-20ppm, actually hard to read off the colour chart, what is confusing me that in your table I am reading the target nitrate value of <10ppm, but on other websites including Al Sabattas other website exert below, I see figures stated of <20ppm.

So my question is <20ppm acceptable or should I try to keep to <10ppm, the differance between the two values, may mean one more water change a week, at presant my schedule is 80% three times a week.

so I can only say what I consider high… any levels above 20-30 ppm nitrates to me is high for discus….My gold standard is to attempt to maintain nitrate levels less than 20 ppm, ideally less than 10 ppm

[zergling]

Blademan - I'd let the more experienced folks chime in on what is a good target level for Nitrates and/or water changes for 4.5-5" discus.

My discus are slightly older and bigger at 5"-6", and I do daily 50% water changes due to two reasons:
1) My tank has a thin layer (0.5"-1") of sand and is lightly planted.
2) I've seen in person the beauty of 7.5" discus. I want my discus to eventually get to somewhere near that size.

PS - I do NOT recommend keeping discus in planted tanks. Freshwater planted tanks are hard enough on its own to keep algae free and thriving. Only experienced hobbyists know how to handle that AND all the eating and pooping that discus will bring.

[Jnotjane]

Wow! those expanded tables are a real eye-opener! You simply cannot argue with math. and having kept a 90 gallon high-tech heavily planted and stocked (no discus) tank in the past, I can tell you that when I kept up with weekly 75% water changes, and trimmed the plants and very carefully did not overfeed, the tank was gorgeous with clear water and no algae - BUT - the angelfish were stunted, and I frequently lost fish. But the tank LOOKED healthy. What I and many others who keep planted tanks failed to realize is that the plants simply cannot keep up with that continual addition of wastes, even with multiple canister and HOB filters (I had 2 eheim 2217's and an aquaclear 110 on that tank).

Long story short - NOTHING can replace frequent water changes.

[dprais1]

Wow! those expanded tables are a real eye-opener! You simply cannot argue with math. and having kept a 90 gallon high-tech heavily planted and stocked (no discus) tank in the past, I can tell you that when I kept up with weekly 75% water changes, and trimmed the plants and very carefully did not overfeed, the tank was gorgeous with clear water and no algae - BUT - the angelfish were stunted, and I frequently lost fish. But the tank LOOKED healthy. What I and many others who keep planted tanks failed to realize is that the plants simply cannot keep up with that continual addition of wastes, even with multiple canister and HOB filters (I had 2 eheim 2217's and an aquaclear 110 on that tank).


Long story short - NOTHING can replace frequent water changes.


agreed
I had a tank with a lot of plants, some decent lighting and DIY co2, I had a considerable amount of floating plants as well. plants gre really well, throwing away handfuls of red root floaters and water lettuce. My nitrates, and I'm assuming doc, would still skyrocket with out water changes. i think most people who think plants will make any significant impact on the water's nitrates concentration are kidding themselves, especially in a system that continually adds more every day.