Big water change VS. many small ones

[Aquaph8]

I hear people advise doing a large water change to fix issues all the time. Ive always been against large water changes and would rather see people do a small change everyday of the week. I just feel with large water changes your changing things too quickly and you can just make the problem worse. Even when matching some elements there are many elements in salt water we dont test for and you never know what else you may be changing about the chemistry of your tank. I would love to hear everyones thoughts on this.

 

[FateX8]

i think what people mean in terms of large water changes is if something is catastrophically wrong where small water changes over time would be too late of a fix
if youre talking about regular water changes then yes smaller water changes is better as long as you can do it without disturbing the display too much

 

[SaltWaterDave]

I'm a fan of smaller WC's more frequently. I like to do one every 2-3 days. I think it helps with stability with less drastic of a change in conditions like a large volume WC does.

 

[myzislow]

I do small water changes, sometimes up to two per week. Never been a fan of large water changes every once in awhile as part of a regular maintenance regimen.

However, if something catastrophic happened and the system was crashing then larger water changes are a must IMO.

 

[wysiwyg]

i do 20% water changes bi weekly on my 180g ds

 

[Reef Breeders Verified Sponsor]

10% every few weeks. I tried an about water change system to do a gallon a day, but it was a little buggy.

 

[mallorieGgator]

I do 20% once a week and things seem to be fine. However, if I could I would do 3 small changes a week. I just don't have that much time.

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[mcarroll]

i think what people mean in terms of large water changes is if something is catastrophically wrong where small water changes over time would be too late of a fix
if youre talking about regular water changes then yes smaller water changes is better as long as you can do it without disturbing the display too much

+1

-Matt

 

[Aquaph8]

I understand what your saying but I also think people panic, change a bunch of water really quick and throw things even more out of wack.

 

[AJreefs]

I understand what your saying but I also think people panic, change a bunch of water really quick and throw things even more out of wack.

Agreed; when livestock are already in a state of shock even large water changes in an emergency is causing even more fluctuation and most likely adding to the problem. If corals are shocked or doing poorly I am a fan of doing many small water changes to correct the problem over time; its hard to think that way when your prized corals/ fish are at risk but it makes sense to me.

 

[Loki]

I have thought about that, but most people will say hurry and change 50% now!

 

[Ace25]

Small regular water changes are always better in terms of stability vs large ones, but large ones do have their place under certain conditions.

As an example of how doing large water changes can work under the right conditions, I have a friend who had a 110G reef tank. He had neglected it for over a year, no water changes, inadequate filtration, and no testing. The tank was over run with algae and cyano. Upon testing the water, nitrates were over 200 and phosphates were over 2.5. Small water changes would have cost more and taken much longer to fix the problem. What he ended up doing was back to back 90% water changes daily over the course of 5 days. 100G a day. First day it knocked nitrates down to 160, second day down to 100, 3rd day down to 40, 4th day down to 20, and finally by the 5th day it was stable under 10 and no longer leaching out of the sand and rocks. The fish and corals (all soft corals) responded favorably after each water change and nothing was lost and after just a week of work, and a lot of $ in salt and RO/DI water, the tank looked pristine again.

 

[strange33w]

I have always been a fan of small water changes. For me over the years I have had better success keeping my tank stable. Plus for me it makes it easier to do the water change so I stay on top of it even if I get a little busy.

 

[BarbH]

I think that as others have said small water changes are the best. From what I have been learning stability is the key in keeping a healthy tank. I understand the concept if doing a large change in the event of something catastrophic happening in the tank, but does make me wonder if it would cause more stress to the livestock that is already stressed out? For those who would recommend doing a large wc in what instances would you recommend doing so?

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[Steelerfan747]

I do a little over 10% every 2 weeks but have done more and more frequently when I've noticed something off

 

[AquaWorldPSC]

I always do a small water change daily. A very small amount, about 3-5% daily.

 

[Thatgrimguy]

Everyone nailed it IMO. For maintenance, regular consistent water changes (I auto change 1% daily) and if something is wrong I have changed 10% 2 times a day for up to 5 days straight (on my 250g actual water volume tank) On my 30g I have been known to do a 90% w/c because I'm taking water directly out of my 210 display and into it anyhow so I know the temp, and parameters are dead on anyhow.

 

[lpslover]

I would have to agree that stability is wonderful. Usually I do 20% every two weeks.

But I have also helped rehab a couple tanks that were severely neglected and on the verge of crashing. These tanks smelled stale and faintly fishy with NO3 levels exceeding 50ppm and PO4 levels above 2ppm, algae all over the place, an unending supply of sludge in the substrate and water so yellowed that you could hardly see from one end of the tank to the other. In cases this severe, huge water changes are the only way to go IMO in these cases. While the sudden change is stressful to the livestock, I think it is far less stressful to get them into cleaner water immediately than to allow them to continue to marinate in toxic sludge. I do think you have to be careful to match temperature and specific gravity at bare minimum.

While more controversial I don't think we should completely write off massive water changes as part of a regular maintenance routine. I have heard Anthony Calfo routinely drains his tank down to a couple inches and refills. He apparently has amazing growth on his corals. Also of interest is the "Ecoreef Zero" highlighted on reefbuilders.com. The system does not get any dosing or maintenance to speak of other than a 100% water change every 6 weeks. The elegance coral in the tank has reportedly tripled in size in the two years the tank has been maintained this way.

Just this last week I did a large water change on one of my tanks. It had been eating through GFO like it was going out of style, and given that the tank is a low flow softy tank and has been up and running for just over two years with basic biweekly maintenance, I decided during my annual maintenance this past week to pull all the base rock, scrub it down and vacuum the substrate to within an inch of its life. I suspected that the sudden and unrelenting rise in PO4 production was likely a result of too much trapped detritus. I pulled amazing amounts of sludge out of the tank and this resulted in about a 60% water change. The corals were of course stressed and looked horrid the day after, but the following day they looked better than they've looked for months. So I think large changes have their place, even as part of a relatively regular maintenance program, especially where as with my tank you can get to the root of a potentially disastrous nutrient build up before it starts to severely impact the health of your livestock. I think the key is understanding the costs and benefits and making an informed decision based on what is going on with the tank in question. Huge water changes are not a cure all, and I think people can cause more harm than good when they assume that any problem they are having can be fixed with a massive water change, but water changes and their attendant substrate cleaning are still the single most effective tool IMO for dealing with large nutrient build ups.

 

[crackers]

I read in a blog a few years ago that J. Sprung wrote and said that 1% daily is the way to go but imo its not something that everyone is willing to do because of bust schedules. I personally change about 10% a week with no problems.

 

[beaslbob]

This water change question is very common.

So let me give a more unemotional math type anwser.

consider this

concentration before water change=concentration in replacement water+(concentration change between water changes)/fraction of water changes.

So if you change 1/10 of the water with 30ppm water and there is a 20 ppm increase between water changes you get:

concentration before water change=30ppm+(20ppm)/(1/10)=30ppm+200pm=230ppm.


If you're interested consider water changes that are %1/day or multiples like 10% ever 10 days, 20% every 20 days etc.

And the water as 0ppm nitrates and the tank is increasing nitrates a 1ppm/day.

What would be the nitrates centration before water changes?


answer 100ppm for all possibilities.

the amount after with water change would vary more as stated above.

So to me, much flames on other boards, and poo-hooed by experts what is important to me is to get the 1ppm increase down to unmeasureable levels. When you do that nitrates are just unmeasureable all the time regardless of wter changes.

And to buffer calcium/alk/mag so they are not dependant on water changes as well.

So I ran my tanks ran for years with no water changes.

my .02