Are water changes really necessary?

[Todd A.]

I've been dabbling in the hobby for a few years now, currently a 210 gal (250 total vol) DT; mixed reef, fish, live rock, etc. And like any good reefer, I work hard to make my tank thrive.
But this just crossed my mind; if all of my water parameters are stable, what is the sense in doing water changes? I've pretty much spent every other Sunday for the last 3 years doing water changes, but almost think I'm wasting both time & money. If my nitrates are >5 ppm, phosphates >.25 ppm, the nutrients must be in check. And if the Ph, Mg, Cal, Dkh, etc are all within the desired ranges (with assistance from additives), it would seem that the aquarium water is stable and sustainable. So hasn't the introduction of these additives, along with proper filtration kinda replaced the need for regular water changes? I'm eager to hear any and all opinions.

 

[Goodair]

I'm curious aswell. Water changes are meant to be a nutrient export and a small import. But if there isn't much to get rid of, is there really a need to do one periodically?

 

[sfin52]

My corals and fish seem to do better when I change the water.
Or maybe its just me believing that.

 

[DQM5]

I think it's better for the corals. Replenish elements imo

 

[Sallstrom]

Here's a picture from a tank at my work. It was five years since we did our last water change :)

So I agree on "why change water if the water is good".
We use Triton additives, calcium reactors and do ICP tests to track our parameters.

 

[Todd A.]

Wow, beautiful tank.
I recently (6 mos) up sized from a 90 to the 210 and have struggled with the tank stabilizing. It took about 2 years before the corals in my 90 were really taking off and assumed it was mostly learning curve. But even after applying everything I learned in setting up the new tank, the coral growth just isn't there although all water parameters are spot on. I had a bad case of GHA that is just now under control, even after 2+ months of zero nitrates or phosphates. It seems that tanks just need some "seasoning" and I wonder if regular water changes inhibit or help the process.

 

[VSVP bet]

I havent done a WC on my 125 in 5 or so months, and i also run no filter media, just skimmers and a fuge. Also my 33 Long is probably coming on a year of no water changes, I just dose accordingly, freshwater top offs, and monitor my live stock. The 33l is softie dominant, the 125 has everything you can think of.

 

[beaslbob]

I've been dabbling in the hobby for a few years now, currently a 210 gal (250 total vol) DT; mixed reef, fish, live rock, etc. And like any good reefer, I work hard to make my tank thrive.
But this just crossed my mind; if all of my water parameters are stable, what is the sense in doing water changes? I've pretty much spent every other Sunday for the last 3 years doing water changes, but almost think I'm wasting both time & money. If my nitrates are >5 ppm, phosphates >.25 ppm, the nutrients must be in check. And if the Ph, Mg, Cal, Dkh, etc are all within the desired ranges (with assistance from additives), it would seem that the aquarium water is stable and sustainable. So hasn't the introduction of these additives, along with proper filtration kinda replaced the need for regular water changes? I'm eager to hear any and all opinions.

You're absolutely correct in that with a tank balanced out and stabilized, there is no need for water changes. In fact water changes in that case can only cause problems. I for one am not capable of doing anything 100 times without making some kind of error. LOL

Here is my analysis of the effects of water changes. Consider that 1) something is increasing (or decreasing) at some rate call this "rate of change". 2) the replacement water has some of that things in it call that "replacement water stuff". 3) water changes are done at some constant interval called "interval". 4) and finally some fraction of the water is change called "fraction of change". 5) that thing is a linear measure. 6) and sufficient water changes have been done so that the value before the water changes is the same water change to water change. called value before water change.

For instance:
rate of change = 1ppm/day
replacement water =30ppm
interval=10 days
fraction of water change=1/10

In order for the before water change value to be constant, the amount of stuff removed by the water change must equal the build up between changes.

in the above example the build up= 1ppm/day*10 days=10ppm

Removing 1/10 of that must equal to 10ppm build up. so the tank must build up to 100ppm. then drop down to 90ppm and back up t 100ppm for the next water change.

Additionally the 30ppm in the replacement water with infinite water changes would result in 30ppm in the system

So generally:

So the value before water changes=(rate of change)(interval)/(fraction of change)+ replacement water stuff

In the example:

value before water changes=(1ppm/day)*10days)/(1/10)+30ppm
value before water changes=10ppm(/1/10)+30ppm
value before water changes=100ppm+30ppm=130ppm
After water change 120ppm
next water change 130ppm

with 0 ppm in replacement water it's 100ppm to 90ppm back up to 100ppm

Now if you let the headache subside and do a little thinking:

The driving factor is not the 30ppm in the replacement water but rather the 1ppm/day change.

So to me what is important is to get that rate of change as close to 0 as possible. IMHO that is easily done with macro algae consuming the nitrates plus the algae and bacteria consuming the ammonia. With calcium. alk, magnesium you have to dose. Relying on water changes will never result in constant values.

Also frequent smaller water changes will not reduce where the tank winds up. If you consider the interval as say 1%/day you would will see that the above does still apply for a 10% change every 10 days. But a 1% change every day still results in 100ppm before the changes. But the drop is only down to 129ppm then back up to 130ppm the next day. So more frequent smaller changes do result in less drops after the change but the same amount before the water change.

That being said you could maintain the tank with water changes alone. But just not at values that are realizable to the home hobbiest. You could live near the ocean and constantly pump sea water to your house such that your tank is receiving many water changes per day. Most of us can't do that plus the tank is now completely dependent on the replacement water. Whereas balancing the tank out makes it independent of the water used. It could start out a 0, 100, 500, 1000,1,000,000 or whatever. it still winds up at 100 plus whatever is in the replacement water which hopefully also is not a 1,000,000 LOL. So any potable water is sufficient for nitrates. For delicate corals things like copper can still be a problem from what I hear.

So I just start the tank with macro algaes, dose diy 2 part for calc, alk magnesium, and do no water changes. tanks have ran for 5-6 years that way with a heavy fish load and easy type corals.

still it just my long winded .02

 

[ca1ore]

There are plenty of successful tanks that don’t do water changes; so no, I don’t think they’re necessary. IMO, they were always a concession to lack of information. Now that you can test for most things, the shotgun approach that is the water change can be replaced with something more precise. I also think the CaRx helps to make the water change unnecessary.

Dilution effect on nutrients is also highly overrated.
Far better in my view to employ filtration.

 

[Christopher Davis]

Not if you dose and add trace elements I only do 10-20 gallons every 6 months

 

[VSVP bet]

Not if you dose and add trace elements I only do 10-20 gallons every 6 months

that bubble coral... wow.

 

[Christopher Davis]

that bubble coral... wow.

Beastie of a thing it is. Sends out crazy sweepers.

 

[VSVP bet]

Beastie of a thing it is. Sends out crazy sweepers.

love how the clown hosts it, how old is the coral? (not to diverge from the thread)

 

[ScottR]

If dosing property and checking parameters, no need unless something is out of control.

 

[Reefs and Geeks]

I don't think water changes are necessary, and for about a year I didn't do them because my filtration methods and dosing were keeping all measurable parameters in check. However, I do think that they are beneficial.

When I upgraded my tank to something double in size and of course had to add more water, so sort of like doing a 50% water change as far as parameters would be concerned. I noticed an overnight difference in PE and corals all seemed to start growing a little faster. I originally attributed the change to more lighting, different water flow patterns...etc that were also changed with a tank upgrade. So I went on without water changes for a few months. It seemed like the initial boost I got after the transfer was slowing down, so decided to do a water change of maybe 30-40% and saw an overnight increase in PE again. Seemed all the coral responded very well, so I've been doing water changes every week or two since.

My theory is that there's something in the new water that is being depleted either from my filtration methods, or being used by the coral/fish/inverts...etc that isn't being tested for that makes a difference after it's significantly depleted. No idea what it might be, but I get happier looking coral when I'm doing water changes than when I wasn't. Could also be removing something that's building up that I can't measure.

Again, I don't think they are necessary, and many people don't do them at all or very limited changes. But I've personally noticed a clear difference when I started doing them again. Coral can grow and do well with or without, but could be better with water changes. If you hate doing them, than maybe try extending them, or even stopping them and monitor the tank to see how your coral react. If nothing bad seems to happen, than you can decide if you want to stop altogether or keep doing them. Every tank is different, so the effect on your exact system could be different than other's tanks.

 

[Christopher Davis]

love how the clown hosts it, how old is the coral? (not to diverge from the thread)

4 months give or take

 

[russell13]

Can you have a successful reef tank without doing water changes, most definitely yes. But doing water changes makes keeping your Parameters in line. When I do a water change I’m doing then just pulling water out of the tank, I’m cleaning all the spots in the display that detritus tends build up. Little dead spots in the tank and parts of the live rock. I’ve done both and I can say without a doubt my tank did better when I would do weekly water changes. Even monthly water changes help.

 

[Gregg @ ADP]

Here's a picture from a tank at my work. It was five years since we did our last water change :)

So I agree on "why change water if the water is good".
We use Triton additives, calcium reactors and do ICP tests to track our parameters.

Beautiful tank!

I see both sides of the debate. The ‘no water changes’ approach works fine. Works better the more advanced you are in this endeavor. Works even better once you’ve achieved the coral and other invert biomass that is evident in your pic.

When I do water changes, I don’t do them to change water, per se, but rather to export a bunch of solids that I would just as soon have out of the system and not have to account for. But even when I do water changes, it’s usually only in the 2-4% range.

Having said that, I will once in a while do a substantial water change. I don’t know for sure that bio-chemically there is some massive advantage, but I do notice there is some extra pep out of the corals afterward. Whether that’s from the change itself or just stirring up a bunch of junk in the process, it’s noticeable.

Now, having said that, I’ve never really seen the necessity of doing water changes to ‘clean’ the water in the tank. Plenty of filtration and chem media that can do that.

 

[Js.Aqua.Project]

Personally, I think with some of the more "advanced" filtration methods most of us are using today, water changes aren't always necessary. I only use a w/c as a way to correct a problem exposed by testing that cannot be corrected by dosing a supplement. I generally test everything once a week, more often if there is a parameter problem.

My thought process:

1. Do all of my corals and fish look healthy? If yes, stop here - no w/c. If no, proceed to step 2.
2. Are my parameters within 5% of their target values? If yes, stop here - no w/c. If no, proceed to step 2.1
   1. Can parameters be corrected w/ dosing? If yes, dose - no w/c, wait 48 hours and restart. If no, proceed to step 3.
3. Have any changes been made in the last week? (Ie - photoperiod, spectrum, carbon/gfo, feeding, etc) If yes, stop here - no w/c, wait 1 week and restart. If no, proceed to step 4.
4. Perform w/c. Wait 48+ hours restart.

 

[WVNed]

I don't test or dose anything. I just do water changes. Some people test and dose every day and never do water changes.
Some people do half and half.
There is no one right way. There is a spectrum of things that can work and it depends on what you have in your tank what you need to do.