Can small, daily water changes replace large weekly ones?

[enrgizerbunny]

I think the biggest thing that water changes give you is nice clear water.
I have an aquaponics system that has not had a water change in about a month. Before that it was 2 months. I top off about 10 gallons a week lately. My nitrates are 0 because the plants remove every single bit of them., but my water has a brown tint to it. I don't really care about this because tank is more like a pond. This proves that yes, if you remove the nitrates with plants or another man's you can forego water changes, but there may be some undesirable results.

+1 plastic container and submersible pump, that's what I do, and I hang my siphon out the window.

As far as the "ponds don't empty half their water weekly"comment...

While the turnover rate varies from pond to pond, MOST ponds have some sort of water exchange due to the water source (stream, spring) constantly adding water to the pond and it draining through the dam. This turnover rate weighs in heavily when considering what kind of fish populations the ponds can support. Ponds are also not as densely stocked as our aquariums so this is a really unfair comparison.

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[enrgizerbunny]

Screwed that up somehow with the edit button and the quote button.

 

[BBradbury]

Large, Freqent Water Changes

One more attempt at the benefits of changing a lot of water and changing it often. Water changes are the best, simplest way to prevent diseases of any kind in the tank. Most, if not all problems that happen in a tank are water related. Water changes are the perfect remedy. By following an aggressive water change routine you avoid having to dose medications and whatever else is out there, that supposedly fixes tank problems.

This is a tiny bit troubling, since water changes have been the basis for a healthy tank for all the years I've been in the "waterkeeping" hobby. But, that seems to be the way the hobby is going. Many are moving away from the tried and true methods and leaning toward some of the shortcuts.

A little bit sad.

B

 

[PB_Smith]

One more attempt at the benefits of changing a lot of water and changing it often. Water changes are the best, simplest way to prevent diseases of any kind in the tank. Most, if not all problems that happen in a tank are water related. Water changes are the perfect remedy. By following an aggressive water change routine you avoid having to dose medications and whatever else is out there, that supposedly fixes tank problems.

This is a tiny bit troubling, since water changes have been the basis for a healthy tank for all the years I've been in the "waterkeeping" hobby. But, that seems to be the way the hobby is going. Many are moving away from the tried and true methods and leaning toward some of the shortcuts.

A little bit sad.

B

Not sad at all,
From it's very inception, the hobby has been progressively moving towards that elusive holy fish grail, the completely self sustaining micro-environment.

In reef tank science, that has almost been realized, yet at the expense of a very limited selection/number of livestock that can be housed without over burdening the systems eco-balance.
Why do you think that is a "backwards" move?

 

[Mebbid]

I don't understand what the problem is here. Whether it's a small daily water change or larger weekly water change, they are still being done. There's nothing inherently wrong with a 30% weekly change which is what would be happening in this case.

If someone could spell it out in layman's terms exactly why this wouldn't work I would appreciate it.

 

[trennamw]

I agree, in some instances, with BBs strong strong wording on 50% water changes weekly. Or more. I think new hobbyists run into the most issues, and kill the most fish, by doing too few water changes. If you had to make one rule for everyone, that'd be the one I'd go with too.

However, soooooo many variables exist ... Your tapwater, your livestock, your plants, your feeding habits, age of the tank ... Lots of people do well with fewer changes and some tanks are better off that way.

HOWEVER ... Until you really really understand all the components of water chemistry, are testing religiously, and are aware of the risks you are taking with each method, I'd go with 50% weekly changes.

That's a lot of buckets for me too and I can't afford a python (and don't have a faucet it can connect to) ... So when it's appropriate for me to do a water change without a gravel vac, I have a trick ...

I got 25' of the silicone aquarium tubing and some airline suction cups. It's soooo easy to start a siphon with this. I stick one end so it's at the halfway point on the aquarium and one in the bathtub (or outside in my plants). And I keep an eye on it while I do other things.

Then to refill I reverse the process, putting a bucket of clean water up higher than my aquarium, and letting it siphon into the tank. It has the benefit of being a very gradual change for the fish too ... My tapwater is like distilled water so I add minerals, and I worry about rapid changes in dissolved solids and stuff. And I have sand substrate so a slow stream keeps everything nicer.

The Walstad tank or Barr method uses a very heavily planted tank to maintain water quality, water changes are rare. Each method is slightly different and it's another set of things to understand and troubleshoot and purchase.

But the main answer is no, don't sub small changes for large ones. You might not need a large change weekly but you do need one at some point, and when you're new you should bank on it being weekly.

Maybe B could give us some context by providing more info about his/her specific tank setup.

I have a 29 gallon that Aqua Advisor says is 104% stocked, it has a Penguin 200 biowheel filter. Stock is a variety of small tetras and rasboras, with danios, Otos, and Pygmy loaches. I have ghost shrimp and I've let pond snails and Malaysian trumpet snails stay ... They all help clean up, along with the Otos and loaches.

My substrate is sand with a little gravel, and I have 3 each of crypts, anubias, and java ferns, all small.

Since my water is almost distilled I've used 1) crushed coral and seachem equilibrium or 2) small doses of cichlid salts and buffer,... GH is about 6, KH 3-4, pH around 7 and stable. Temp is 76. I finished a fishless cycle in April and stocked about 25% per week.

I feed New Life Spectrum Thera A, and Omega One algae wafers, and watch the tank bottom for clues that I'm over feeding.

At first I did weekly 50% changes, now I do 30% every 2 weeks. I use a TDS meter to watch for stability too.

I use the API test kit, plus GH and KH bottles. For pH I use a wide range hydroponic test kit as our LFS recommends.

I haven't lost a fish in that tank, I have never seen ammonia or nitrite on a test. Nitrate has never topped 5 and is sometimes undetectable.

My smaller tanks get more frequent changes and their happy balanced spot has a pH close to 8. I have gotten blue green algae in my 3 gallon, it seems to be a phosphate thing as daiky changes doesn't help.

I use fragments of root tabs for my crypts but otherwise don't fertilize. Light is low LED light.

So that's more than you asked for but maybe if a few others do the same you'll get the context.

I'm convinced that the combo of invertebrates, softer water, and a super high quality food, have a lot to do with my not needing more water changes.

 

[trennamw]

Also, it's simply not true that large frequent water changes have always been the mainstay of the hobby.

There's a fantastic book by Boruchowitz on freshwater fishkeeping, he is passionate about water changes too but is clear that when he first started keeping fish, it was thought that you should NEVER change fish tank water because new water kills.

With understanding of the nitrogen cycle and other things, it became the good standard to do huge frequent changes.

It's pretty common for things to go to one extreme, then another, then balance out. I'm not surprised the trend these days is to find a nuanced answer to water changes, that isn't one size fits all.

Unfortunately some important aspects of water quality aren't easily measured at home except by fish health. Also newcomers need more black and white rules, and ones that account for the fact that most everyone does a little less than the rules say.

For the OP, here's a chart that illustrates the difference between small and large changes. It presumes a 100 gallon tank so sub the word percent for gallon. View attachment 241704

Well actually maybe we are all wrong. 8 10% changes leaves 44% old water, and a single 50% change leaves 50% old water.

Maybe someone with excel can run the numbers on a tank that's likely to go from 0 to 10 nitrates in a week and see if it's comparable.

 

[trennamw]

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Credit for the book (and suggested reading, though it's too old to have fishless cycling) ...

 

[Mebbid]

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View attachment 241705

Credit for the book (and suggested reading, though it's too old to have fishless cycling) ...

View attachment 241706

That's a really strange way of looking at things. In fact, we had a long long debate on the saltwater forum about this a while back.

What it basically came down to is this: The amount of "old" water left in a tank doesn't really make much different, it is just h20 after all. Everything in that h2o that's left in the tank i dilluted with all of the new water you put in. That means all of the undesirable stuff in the old water is dilluted as well. It doesn't hold more bad stuff than the new water due to this fact.

In short, "old water vs new water" is just a mathematical way of looking at something that and trying to give reasoning to it which doesn't necessarily make it right considering the nature of it all.

 

[PB_Smith]

I agree, the logic that the book uses looks good on paper, but doesn't really convey the reality of the water chemistry as Mebbid pointed out.
And how old is that book? When I was managing a store, 30+ years ago fishless cycling was being done by some folks.

The main things we try to accomplish with a water change is;
reduce nitrates/phosphates-- can also be handled biologically
replenish trace elements---can be done by using specific substrates and rock
maintain ph---same as previous
removing excess detritus/mulm/bacterial flock---really can only be done with water changes, but the degree/frequency is determined by the type and size of the bioload

I feel the biggest determining factor is the livestock you're keeping.
Some critters love big frequent water changes, others not so much.
I recall a friend who bred discus years ago, wild caught ones. His tanks were total blackwater tanks, like they were just carved out of a south American river, and if he did more than 5-10% at one time, the discus would totally freak out. I'm sure 50% would have killed them. That was using water that for all intents and purposes was chemically the same.

Bottom line is if your critters are all doing good, healthy and happy and so are you, than whatever regime you have established is working.
There are no rules carved in stone about fish keeping, just common sense.

 

[Mama Karoti]

Sorry to repeat, but I feel it's warranted. 5% daily is equivalent to 30% weekly. It is chemistry and mathematics. There is nothing mystical going on in our aquariums. So yes, to answer your question. It is fine to do daily small water changes that by the end of the week will replace the equivalent amount of water that a weekly water change would.


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[allysonwonderland]

Sorry to repeat, but I feel it's warranted. 5% daily is equivalent to 30% weekly. It is chemistry and mathematics. There is nothing mystical going on in our aquariums. So yes, to answer your question. It is fine to do daily small water changes that by the end of the week will replace the equivalent amount of water that a weekly water change would.


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Finally got around to figuring out the math today, actually! For me, the trade-off between ease and that 5% that didn't get changed out is worth it. I can even do multiple little changes a day if I need to, still easier. Thanks for clarifying though.

In case anyone is curious, here's a chart I made comparing the two methods for my tank, by number of buckets (which, for me is 5%). Column A is the normal method. If I lug 5 buckets back and forth, I have changed 25%. Column B is the method of taking 5% out, then filling right back up with clean water. I can do this once a day to get to 30% a week as Mama_Karoti said, or do it a few more times to go higher. Of course, the difference gets bigger and bigger as time goes on, so if I needed to do a large change, it makes much more sense to just get it all over with in one shot.

Edit: Thinking, now though, that the percentages are going to be a little different than what I have in the chart. If I did twenty 5% changes in one day, then yes this is right. But my fish produce nitrates every day, so that new water from yesterday isn't so brand new anymore. I don't even know how to math all that out.

 

[Mebbid]

It's really not worth trying to figure out old vs new water out at all.... even a little. Mathematically it sounds right but that's just not how it works.

 

[allysonwonderland]

that's just not how it works

What do you mean?

 

[Luananeko]

Basically, its a calculus problem to figure out small changes impact on water parameters vs one big a week. Can it be figured out? Sure. Is it worth the time to calculate out properly? Ehhh probably only if you enjoy that type of math

 

[jetajockey]

Get a python.

 

[Caliban07]

It seems that many would agree that altering the fishes environment drastically and rapidly can have an overwhelming physiological effect on the fish. Of course this may be tolerated as already mentioned but it can't be as good as maintaining stability.

You can still maintain stability by doing 50% weekly water changes if variables such as diet, feeding frequency, water change frequency, stocking levels etc remain the same. Fish will become accustomed to this pattern. And toxins will remain stable.

If people understand that fluctuating water parameters is bad then why is there not more focus on measuring TDS (freshwater) and constantly rising TDS levels. My thought process is, the longer the TDS rises surely the more sensitive to water changes the fish will become?

How do ponds that only receive rainwater combat TDS? How are these things removed. Is the TDS in natural ponds etc constantly rising and if so do the fishes inhabitants even care as they are used to it?

In an enclosed system, surely this is much more critical. And you can only manage TDS by doing a 100% water change every so often (years) this would not be good for fish though right?

At the same time, I know of people who have kept fish for years without running in to this problem. I just feel it needs more attention.

 

[Delapool]

Sorry to repeat, but I feel it's warranted. 5% daily is equivalent to 30% weekly. It is chemistry and mathematics. There is nothing mystical going on in our aquariums. So yes, to answer your question. It is fine to do daily small water changes that by the end of the week will replace the equivalent amount of water that a weekly water change would.


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I just did this on the train using assumed 100ppm nitrates and got the same I think. Daily 5% changes would reduce nitrates to 70ppm while a weekly water change of 35% would take it to 65ppm. Does that sound right - less difference than I thought.

I'm going to have a toe in each camp. I agree if you have got all the gear out, then do a large pwc. In my case on the bucket brigade that's about 50gal shifted for 35%. It takes about 35gal just to cover the gravel vac so this works for me.

On small tanks I'm trying smaller, more regular pwc's. The maths says it shouldn't matter but I'm hoping this works out better stability wise. And I'm hoping it will be easier

 

[Luananeko]

Okay.... Assuming you start with 50 nitrates at the start of the week and your fish generate 15 nitrates per day. Since your fish generate 105 nitrates during the week (7 days x 15 nitrates a day), and you started at 50, the nitrates would have been at 155 if you had done no water changes.

Since your fish generated 105 nitrates during the week (7 days x 15 nitrates a day), and you started at 50, the nitrates would have been at 155 if you had done no water changes.

A 5% water change would do this (rounding to nearest .01 and assuming no other sources of nitrate reduction):
Day 1: 50 nitrates - 2.5 = 52.5
Day 2: 52.5 + 15 = 67.5 - 3.38 = 64.13
Day 3: 64.13 + 15 = 79.13 - 3.96 = 75.17
Day 4: 75.17 + 15 = 90.17 - 4.51 = 85.66
Day 5: 85.66 + 15 = 100.66 - 5.03 = 95.63
Day 6: 95.63 + 15 = 110.63 - 5.53 = 105.1
Day 7: 105.1 + 15 = 120.1 - 6 = 114.1

That's roughly a 26% reduction, compared to a 35% reduction if you did the same amount of water changes all in one go.

 

[Mebbid]

Okay.... Assuming you start with 50 nitrates at the start of the week and your fish generate 15 nitrates per day. Since your fish generate 105 nitrates during the week (7 days x 15 nitrates a day), and you started at 50, the nitrates would have been at 155 if you had done no water changes.

Since your fish generated 105 nitrates during the week (7 days x 15 nitrates a day), and you started at 50, the nitrates would have been at 155 if you had done no water changes.

A 5% water change would do this (rounding to nearest .01 and assuming no other sources of nitrate reduction):
Day 1: 50 nitrates - 2.5 = 52.5
Day 2: 52.5 + 15 = 67.5 - 3.38 = 64.13
Day 3: 64.13 + 15 = 79.13 - 3.96 = 75.17
Day 4: 75.17 + 15 = 90.17 - 4.51 = 85.66
Day 5: 85.66 + 15 = 100.66 - 5.03 = 95.63
Day 6: 95.63 + 15 = 110.63 - 5.53 = 105.1
Day 7: 105.1 + 15 = 120.1 - 6 = 114.1

That's roughly a 26% reduction, compared to a 35% reduction if you did the same amount of water changes all in one go.

He generates 15ppm weekly rather than daily.