Water Changes: What "percentage" makes it worth doing?

[carbasaurus]

It depends on what you are trying to accomplish and just comes down to simple math. If your goal is to reduce nitrate and say your nitrate is 40, a 20% water change only gets you to 32. You would need to do very frequent water changes at that volume to have a meaningful impact. There are other better ways to reduce nitrate load.

If your purpose is to replace trace elements for coral health then maybe 20%???? But even for this purpose it’s just guess work without advanced testing.

I still do water changes periodically despite my above comments. It’s an excuse to vacuum up any Cyanobacteria lurking in crevices, clean up the sand, give a good flush of the dead zones, clean the sump and inspect all my gadgets

 

[Paul B]

I have always felt that to many water changes or changing to much water was detrimental to tanks as water, within reason gets better with age. That is one reason older tanks have no problems and new tanks with all new water look lousy and are never healthy.

 

[RicksRed66]

As anyone heard of doing a 80--90% water change? my " Fish Guy" did that to our reef tank & it seemed a bit too drastic a change...

 

[beaslbob]

As anyone heard of doing a 80--90% water change? my " Fish Guy" did that to our reef tank & it seemed a bit too drastic a change...

While it is possible to maintain a tank through water changes, it's not practical for the average hobbyist hundreds of miles from the ocean. To those people a balanced out ecosystem is the only practical method.

But if you live on the beach and can constantly recirculate ocean water, go for it.

my .02

 

[costaricareef]

1.25% per day AWC with DOS.

 

[carbasaurus]

As anyone heard of doing a 80--90% water change? my " Fish Guy" did that to our reef tank & it seemed a bit too drastic a change...

I read in Coral Magazine a few years back that people keeping pico reefs (like 1 gallon systems) do just that. Once a week they would feed the corals then do basically a full exchange. Some of these tiny reefs even had sps corals. The trick of course is making sure salinity, pH and temperature are matched

 

[Stigigemla]

I can see 3 reasons to make a water change.

1. If there is too much of anything like Nitrate or phosphate a big water change can reduce the value of it.

2. If something is depleated like a trace element You can often notice a change 2 days after a small water change like 10%. 10% of an element is more than a 1000 times more than zero.

3. It can make the owner feel good because a good thing for the tank has been done. That works even when the water change was unnecessary.

 

[AquaticOttawa]

20% weekly. Tank is heavily loaded.

 

[Subnautica]

Who's the lady in the original post? Asking for a friend of mine.

 

[Joekovar]

I change 10G in my 55G every weekend after stirring up the sand bed and hitting low flow areas with a toothbrush.

If I don't, I get algae outbreaks that take 1-2 months to get rid of.

 

[Gup]

I am lazy and use the APEX DOS to do it for me. I change 5 gallons a day during the over night hours on a 675 gallon tank, works out to about 20% a month. All I do is mix salt once a week. I believe the tank is as stable as it ever has been.

Of course, it's whatever works for you or each one of us for that matter

But I have a serious question. If you change 5 gallons every day, you're pulling out completely good water everyday. Granted, it is miniscule, nevertheless you are still draining healthy, good water molecules, not to mention the nutrients embedded with your fresh salt. No?

 

[Gup]

My 55 gallon is 6 months new. My wife and I have the water changes down to a science now. The drain and refill requires just under 20 minutes. I'm still changing 20 gallons every 4 - 5 weeks. Depending on our availability.

The day prior, it takes me about 20 minutes with the setup of the new water.

 

[Gup]

I change 10G in my 55G every weekend after stirring up the sand bed and hitting low flow areas with a toothbrush.

If I don't, I get algae outbreaks that take 1-2 months to get rid of.

Would you consider Dino X? I used that after just a couple months, and it right up. I did just develope a red cyno problem about a month ago. I used the red cyno Chemiclean & it cleared that problem up in 4 days.

 

[Joekovar]

Would you consider Dino X? I used that after just a couple months, and it right up. I did just develope a red cyno problem about a month ago. I used the red cyno Chemiclean & it cleared that problem up in 4 days.

Would you consider Dino X? I used that after just a couple months, and it right up. I did just develope a red cyno problem about a month ago. I used the red cyno Chemiclean & it cleared that problem up in 4 days.

The main good that comes with regular water changes vs chemical reactions for me is removing things in multiple stages of decomposition because I'm stirring everything up pretty well before pulling water out.

Whereas with chemicals specific stages of decomposition get targeted for chemical reactions.

If I didn't emulate strong tides, storms, and other weather by stirring everything up periodically, some of the higher up in the food chain elements would build up and eventually overwhelm some stage of the system when they finally break down.

 

[beaslbob]

Of course, it's whatever works for you or each one of us for that matter

But I have a serious question. If you change 5 gallons every day, you're pulling out completely good water everyday. Granted, it is miniscule, nevertheless you are still draining healthy, good water molecules, not to mention the nutrients embedded with your fresh salt. No?

yes.
what happens is that system builds up to where the waterchange removes the build up between changes. you change 1/10 of the water it builds up 10 times the change. 1/20 20 times. 1/5 5 times and so on.
the best thing is to limit the buildup .

 

[Randy Holmes-Farley Verified Community Expert]

Of course, it's whatever works for you or each one of us for that matter

But I have a serious question. If you change 5 gallons every day, you're pulling out completely good water everyday. Granted, it is miniscule, nevertheless you are still draining healthy, good water molecules, not to mention the nutrients embedded with your fresh salt. No?

I'm not sure what a good water molecule is vs a bad one, but doing 6 changes of 5% each does exactly the same as one change of 26.6%.

Thus, it doesn't matter that much how you change 20-30% per month. Even 300 changes of 0.1% each is nearly the same (like one 25.9% change).

.

 

[Laith]

AWC of 1% a day.

 

[Daniel@R2R Verified Admin]

Dear Abby,

I was told that water changes have a positive effect on my aquarium but what percentage of water should I change to make it worth it?

Sincerely,

Confused Reefer

image via @Reef Hacks and their Exploring Water Changes article.

Hmmm...I'd say it depends on how often you change it. If once a week, I'd say at least 10%. If once per day, make it at least 1-2%.