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

[DeniseAndy]

Wait, you only do a partial water change? I like to do 100% when I can. Okay, only for my 6g and 20g and sometimes 40g. Those guys do not have a calcium reactor attached. My 210g I do when I feel like it every month or so maybe 10-20%

I always recommend new hobbyists do water changes weekly though. It gives them a chance to really spend time with the tank and measure and get used to how the corals adapt and just everything. You need this when you first start out to get good. No soccer player just walked onto a field at 20 years old and played pro ball without some experience. Jsut saying. Baby steps to jumping out of airplanes is not really recommended.

 

[Billldg]

If I do a massive water change at one time, it will be at least 25 percent of my 225 gal tank. As of right now I am doing a 3 gal daily water change.

 

[Jcascioli]

225 Gal system, SPS dominant, 2% per day changed out to replace trace elements.
Thanks DOS!

 

[Borg]

fish only here,
100-130 gallons a week on my 180.
roughly 60-70%

nothing is better than a good old water change.
I find them relaxing

 

[BlueZreef]

AWC Via DOS

2 gal per day on 210 gal tank. With a 75 gal mixing tank, I go out about once a month and mix up a batch and that’s it. Easiest/most stable tank I’ve had (Trident does 2 part dosing as well).

tried no WC in the past, seems like something would always creep up unnoticed until it was an issue. AWC seems to avoid this all together.

 

[spd3001]

I have an AWC system on a mixed reef DT and I do 2 gallons per day (~2%.) That gives me an effective water change of 50% per month. It's on a 90 gallon DT with a sump. Giving allowance for all the sand and rock, the system has about 90 gallons of water. I just got the AWC system up so I'll run it like this for a year and see how it goes. If anyone wants to calculate the effective water change amount for a series of small changes, you can do that here:

Effective Water Change Calculator

Aquarium calculator; Estimate the effective water change amount of several combined smaller water changes.

www.hamzasreef.com

 

[Itsadeepbluesea]

I wouuld say any depending on the need.

 

[Buckster]

I change 20% every two weeks in my 180. The in between weeks I change 20% in the 32 biocube and the 30 QT.

 

[Worthy1]

Such an area based on variables. Depends on the tank setup. No Nutrient removal or trace element dosing and water changes are the only answer. If that area is covered then you dont have to do water changes at all (unless you have a problem).

I am surprised by 10-20% being the most common answer though. BRS said it best one time. All you are doing is removing 10-20% of the problem or replacing what is depleted. 80%-90% is still present. Makes you really wonder how effective it is.

Personally the 20% water change i think is one of those remaining 'bro science' aspects from reefing from back when filtration wasnt great, supplements were non existent etc. Everything those days was 'in the salt'. I dont think it is as effective these days (which BRS attest to), its more of a placebo effect. If you have the opportunity to save money and time on water changes by setting up your tank properly then why not. Sure if you have a nano or a tank that needs it then its no diff to why it was needed years ago.

 

[Skibum]

No water changes unless one of my kids dumps something into the sump.

 

[Bouncingsoul39]

when i was a spry young lad i used to do 10% weekly and it worked well. Now that my spirit is broken, I do 25% every 2-3 weeks.

 

[mauisue]

Per the recommendation of My Fish store they come and pull close to half the tank of the 93 gallon tank once a month and refill with new water.

If this is not correct would like to know as I started my Red Sea 350 tank in October of last year as a newbie.

 

[bronzewhaler22]

I do 15% a fortnight for mine (1200g)

 

[blasterman]

Over a year now in my 20L with no water changes and no skimmer. With such a small tank I have no room for error, but I don't seem to have a problem with growth.

And for the millionth time salt mix makers have no concensus on trace elements nor what constitutes a trace element nor how much trace elements to use. ICP tests on raw salt mixes are all over the place.

That's fine if you like to do water changes, but please stop using the trace element excuse.

 

[Ninic Luka]

i do about 8% weekly only to syphon out detritus

 

[Cunning_plan]

Never done a water change on my tank. Keep everything to NSW with dosing and ICP. Nutrients handled by a big fuge, skimmer and GFO.

That lovely clean water feeling I used to get from changing water I now have all the time by running carbon. If something has gone badly enough wrong that I need to change water, 10% isn't going to help me much...

180 gallon, mixed reef.

 

[PhreeByrd]

The math gets kind of tedious, but it's probably enough to say that with every water change, you are removing, along with old water, some of the new water you added during your prior water change(s). Unless you do a 100% water change, there will always be old water in your tank, and you will always be, to some degree, wasting reasonably new water you recently changed.
A 10% weekly water change isn't really changing 10% of the old water. A 2% daily water change does not mean that after 50 days you will have replaced 100% of the water. Only a periodic 100% water change can do that -- and for most of us, 100% water changes are simply not feasible.

I did 25% every 2 weeks for years, but for the past couple of years I've been changing 25% every 4-5 months. The tank and the fish have not suffered a bit for that change of schedule. I can't say with any confidence that this is a good Rx for anybody else, though.

 

[Randy Holmes-Farley Verified Community Expert]

The math gets kind of tedious,

FWIW, I posted a table of exact calculations earlier in the thread. Copied again here. In this range of a total of 30% changed, it makes little difference how you change it. I agree that if you are doing massive changes all at once, that can accomplish more.

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

 

[beginner_reefer]

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.

Same. We do a 10-20% water change on our 100 gallon every 2 - 3 weeks just depending on how the water column and sand bed is looking. Have been up and running almost 4 months now and have never vacuumed or cleaned the sand bed. Only have GSP at the moment with 5 fish and a CUC. Hopefully it doesn't come around to bite us in the rear without cleaning a DSB.

 

[GeoSquid]

180 gallon softie tank change ~5% a month. Sometimes I use artificial mix and sometimes I use NSW from scripps pier birch aquarium. I used to change more but corals weren't doing as well. Once I started changing less corals really took off.