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

[revhtree 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.

 

[lapin]

Not only are you removing waste but are replacing other elements with new salt mix water.
Personally I do 10% per week.
Each tank is different as to how much a change will be needed. Every bit helps

 

[Geventh]

After every water change, tank looks stunning and it gives me an opportunity to spend time with my tank.
I do 10 - 15 % every week.

 

[Waters]

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

 

[Ocean’s Piece]

I do 15% water changes (5 gallons) on my 32 gallon Biocube every week.

 

[PeterC99]

Doesn’t the frequency of the water changes impact the decision on the quantity of the water change?

 

[Gary Inwood]

I do 15% water change every two weeks on my 660L system

 

[Gtinnel]

Doesn’t the frequency of the water changes impact the decision on the quantity of the water change?

I agree 100%.

I'm not sure how to answer because I do a 1.5% water change every day. So to answer the question are we basing it on that percentage every week, every month, every day.....

 

[kzenoni]

I have a 350 gallon which I do 10% (35gallon) every two weeks and a 200 gallon fowlr that I do a 10% (20 gallon) once a month since the fish are not as sensitive as the corals.

 

[Bpb]

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

 

[GoTakeANap]

I am currently doing 20% water changes every 2 weeks. Corals are extremely happy after a water change. Maybe I need to change my schedule and do 10% every week.

 

[WVNed]

2% every day

 

[DDenny]

Right now I’m doing 1.5G every week that’s 43%. Working on getting that same change to every two weeks.

 

[punchy7080]

Currently doing ~10% per week on both of my tanks

 

[tyryfin]

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.

 

[ReefRxSWFL]

Water changes are extremely important … for the first 2 to 3 years a tank is up and running. After that ,it depends on tank size and style. Style meaning how you export nutrients and replace nutrients and major and minor trace. Once the microbiology is established and balanced, and parameters are stable and in target range, there is no need to do water changes when you balance in and out. Of course, if you do continuous auto water changes, thats your thing, which is excellent on smaller tanks.

 

[RMS18]

Salt companies be like ugh another w/c thread.

 

[dbowman5]

i have somewhere around 100 gallons in my main system, i change 15 gallons at a time but infrequently. my bio load is light and have just a small amount of stony corals. my tank seems to be doing well. my FOWLR system is around 35 gallons and it gets no water changes and it seems to be doing well.

 

[madweazl]

I've done 15-20% every week for the past 4 years with good success so I stick with it.

 

[P-Dub]

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