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

[mattgsa]

2% a day. Works for me. Apex DOS makes it easy.

I do the exact same thing.

 

[dross9615]

To misquote Ryan from BRSTV "if you remove 10% you are still leaving 90% of the problem" That is why I think 30-40% is most optimal. but then you would have to get into frequency of changes as well As I would think 10% everyday would be just as effective, if not more than 40% every 4 days. I have yet to see anyone really breakdown this issue but I am sure someone has.

 

[Randy Holmes-Farley Verified Community Expert]

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.

Depends on how often you do it.

Folks with AWC might only change 0.05% at a time, and it works out fine if they do that 20x per day.

 

[Randy Holmes-Farley Verified Community Expert]

I have yet to see anyone really breakdown this issue but I am sure someone has.

It's here:

Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

 

[CanuckReefer]

2-2.5 % every 3 days has kept my system pretty steady over the years.

 

[Timfish]

I do between ~10% and ~80% a month (the ~80% is on a 25 gallon tank and it's just easiest to do a bucket a week). It really depends on the systems livestock and how well they are doing regarding how much to take out.

I started doing weekly water changes on most of my tanks when I noticed a couple systems that got weekly water changes almost always looked better than my systems that only got monthly water changes. The simplistic view I had then was just removal of waste stuff that wasn't taken out by skimmers.

Now I see it in a completely different light after learning how complex the microbial processes are. Now I know algae are dumping hydrophilic stuff that promote heterotrophic (read "oxygen consuming") bacterial shifts in the water and in the coral mucus layer and microbiome (See Rower's presentation here). Corals on the other hand are releasing DOC that promotes autotrophic (read "oxygen conserving") microbial processes in the water around them. Additionally, the different types of animals are promoting different types of bacteria.

Now I see water changes in a completly different light. The reason they worked so well for me decades ago was two fold: First, with small weekly water changes I was often siphoning off algae from rocks and sand, reducing the production of damaging DOC that promoted heterotrophic bacteria. Second, I was directly reducing the bacteria in the water (1 million per ml, see ~1:30) which would be replaced to some degree by autotrophic species promoted by coral DOC.

So how big of a water change needs to be done is largely influenced in my opinion by the types of bacteria being promoted by the livestock in a system. But water changes are essential. Our systems can be thought of as biochemical energy engines. Engines we are constantly fueling whenever we feed. There's no such thing as 100% effecient engine or a perpetual engine. To think we can keep our systems and animals without water changes over the decades or centuries they are capable of living without water changes strikes me as beyond foolish.

 

[optimisticdingo]

As long as my Nitrates are around 5-10 and Phosphate is between 0.05-.01, I maintain 10% a week. However, if those levels get elevated I find the 10% a week isn't enough to lower the nutrient levels. In this case I usually start doing 20-30% a week until the parameters are back in check.

 

[ReefGeezer]

I try to do 10% per week. Sometimes it is 20% every two weeks though if I'm busy. The tank is young and the bioload is increasing. the water changes have a positive effect. I did the same on my old tank that was well established. The effect was not as obvious.

 

[MabuyaQ]

There is no right or wrong answer to this question, even 0% or 100% are perfectly fine answers depending on the circumstances/purpose of doing waterchanges. Sure dilution is the first solution to polution, but you will also dilute things you that don't need further dilution and thus require even further supplementation after a waterchange.

My Zeovit tank always looked worse after a waterchange so I stopped doing waterchanges (always used 75% TM pro reef + 25% other brand or 100% TM pro reef for waterchanges). When not running Zeovit (before and after using Zeovit) the tank sometimes looked better, but mostly the same. Last 5 years running my tank, no regular waterchanges. Only monthly (ICP)testing and the look of the tank triggered me into doing a couple of waterchanges (including a set of 3 times 30% when Nickel suddenly went up due to a rusty magnet).

 

[Arabyps]

I do a 20% (equates to 30-35 gallons) every 7-10 days. It removes waste and replenishes essential elements. As part of the process I also vacuum the sand-bed usually every 2 months.

 

[Sunny in Miami]

I do religiously weekly 15% water changes because I notice it keeps the water so much clearer and the fish seem happier.

 

[srobertb]

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.

You can forego a lot of other husbandry with water changes. 10% weekly either continuously or at one time is a good goal. This isn’t feasible on a lot of tanks due to size or simply because coral uptake happens too fast…so we monitor things either in person or through the mail and add things accordingly in tandem with nutrient export controls.

Conversely a 10 gallon softy or even LPS tank could probably forego a skimmer and additives in exchange for 10-20% weekly water changes.

 

[Cool tangs]

Currently i would say water changes are worth it, im currently doing dialy as i let my nitrates get a little high and oh boy are my corals loving me for it! I use natural salt water, never will i mix again, im way too lazy for bucket salt. I also find the levels to be too high for new corals and stresses them out. I mostly buy freshly taken coral.

In saying that my last tank was a nano that was up for 5 years, i would do 6 monthly water changes only a few lps. Heavy stocked. I ran culurpra in a sump and that stuff sucks up nutrients. This thing was stable af and everything happy. Mind you this was in the real live rock days.

I would say early days water changes are very important, but i plan to reduce this once i gdt everything balanced and rely on other forms of nutrient export and dosing with min W/C

 

[steallife904]

i have a 150. i do a 5 gallon bucket a week. lol. so less than 5 % but it works for me. some weeks i do 10 gallons

 

[vetteguy53081]

I let my fish and coral talk to me regarding water change. If they’re happy, I leave them alone.
Recession, feeding behavior and test results dictate my need and percentage

 

[DH78]

Depends on what "issues" you are trying to resolve and the size of the tank.

I agree. Depends entirely on why you are changing the water.

 

[FrostyFrags]

Used to do 50% for my 8G, but with a fishless and softy only tank I've found they are much happier with the ~15% water change

 

[LosReef]

Definitely no one-size-fits-all answer to that. Depends heavily on what you’re supplementing and what you’re removing via nutrient export and coral consumption. Running aggressive carbon dosing, with phosphate removal, and a calcium reactor using coral skeletons will be running out with the bad — in with the good a lot more efficiently than a low tech tank with just rocks, flow, and fish food.

It just depends on the setup and the coral needs.

I may be wrong but I feel like water changes are best used for replacing trace and minor elements, and/or removing large amounts of toxin/contaminant.

Scenario A would depend (again) on how you’re supplementing to begin with, scenario B would obviously be a “bigger is better” situation.

Too many variables.

On my last sps tank with carbon dosing and calcium reactor I did about 10-20% a week, but that was always performed using fresh mixed water replacing what I’d take out in shipping bags. Rarely needed to just “do a water change” for water change purposes alone.

On my present tank, it’s been up for almost 4 months, very few corals, carbon reactor, and large algae turf scrubber. Phosphate stays down around 0-0.1 with 4-5 time a day feedings so I haven’t performed a water change at all yet

It'll also depend on what kind of problem you're facing. High nutrients, low supplements, accidental high supplements and so on. I had a close call with my Dose failing on. Scraped a baseball size alk pile out of my sump. Took a couple of 50% water changes within a week. Didn't lose anything as I was lucky to work from home at the time and able to fix it.

 

[dross9615]

It's here:

Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

Thank you! Very simply shows that one larger water change is more effective. Though I wonder how specifically involving siphoning hose would effect this. As my thought process is if I am doing more regular water changes I would be removing the poop sooner and keeping it from harming water quality rather than letting it sit for several days in between.

 

[MONTANTK]

I do 10-15% a week. In the coming days I’ll have my AWC set up so I’ll do about 10% a week and then every 2-3 weeks I’ll do a manual water change to export nutrients