The Whole Water Change Thing

If i'm not mistaken, this is wrong. If you change 5 gallons of old water, then you change out a (in this case a 40g tank) 1/8 of all bad stuff. Then next day you change out 5g, then you're taking out 1/8 of the 7/8 that remains except it's diluted further, so you could be taking even less! So for most efficient water changes, lots at once is better. However, you have to look at it from the fish point of view. I think if you broke it down to a two water changes in a week instead of one. This will make the params shift less, but you have your hands in the tank twice instead of once.. which is more stressful? Hands in the tank a few extra times or param changes. If your doing you water changes correctly, the params shouldn't change at all except for taking bad stuff out.

Just my two cents.

Evan.

 

Large (infrequent) vs. Small (Frequent) water changes.

Evan,

I agree with your observation.

Example over 3 days of 5% changes would result in 14.26% water change
If you take out 5% of a 100% concentration on Day 1 (you take out 5%)
You then take out 5% of a 95% concentration on Day 2 (you take out 4.75%) (total removed = 9.75)
You then take out %5 of a 90.25% concentration on Day 3 (you take out 4.51%) (total removed = 14.26%)

Example of 15% water change all at once would result in 15% water change.

As such, The mentioned article is probably the best advice I've seen on water changes. It makes total sense and doesn't get into analysis paralysis on calculations and schedules. It is just common sense from observing the ocean and what it does.

The following paragraph from the article supports large quantity water changes AND that the reef creatures can handle it because that's what they are used to.

Although it may sound remarkable at first to do such large water changes, it is not unnatural by any stretch of the imagination. Is there any better example of the power of dilution than the ocean itself? If you spend any time at all on living reef, you will be astounded to see how much water is exchanged in a moment: millions of gallons of water in flux within sight. Add to that the fact that so many popular reef creatures are intertidal, and we have a good argument to start with for the tolerance of reef creatures to hearty water changes.

The following paragraph indicates that the the larger volume changes also work slightly better than smaller more frequent ones which makes sense because you are removing a "consistent concentration" at one time instead of a "progressively more diluted concentration" on subsequent days.

Informal experiments have been done to compare if larger monthly water exchanges were better for water quality on testable parameters like nitrate than smaller weekly exchanges. In such trials where the same total volume was exchanged either way, the larger monthly water changes actually had a slight edge on the smaller weekly events.

He does admit that no studies on stressing livestock by waiting longer between water changes has been done.

What the statistics do not reflect, however, is the stress of exposing livestock to greater extremes of water quality for longer periods of time by monthly water changes. Greater studies on allelopathic competition in time will undoubtedly, in my opinion, underscore the need for better attention to water quality in marine aquaria.

I generally monitor my water with tests and make changes when they are needed. I just try to keep the water parameters where they need to be and pay less attention to the "schedule of changes". Sometimes I can go longer than a week between changes, sometimes not. Any time I do a water change however, it is at least 25%.

Just my 2 cents also.....

 

This has been my mentality for the longest time. When I do WC's, I do 25 gals(every week) in one shot for my 90g DT and I have never seen any ill effects to any of my livestock. Luna

 

Hey there Buddy I either miss your post or you been deep under cover How is the tank doing .. Well I hope Lights doing the Job for you . I was thinking about yours and customs last week we sent a P/M Bullet skimmer to the U.K for another member here . Love to see some pics. of the tank Don't make me put Luna you for some pic's He is the main photologist here and ruthless I tell you..

 

LMAO Pic Police they call me. Whats your take on this water change Tangster. All at once or a little here and there? Luna

 

my lfs stresses a reef thrives in a consistant enviroment. Seems to make sense, i would rather do more smaller water changes a month than one big one a month. If u were consistantly diluting the water each week with a change then there wouldnt be much of a benefit of doing one big change cause u never let it build up to begin with...reducing stress on the fish. Not to mention the trace elements u are replenishing the water with....the ocean doesnt wash the reef with one big wave or current once a month to replenish elements and circulate the water. I think if we look at nature and try to mimic that to the best of our ability we couldnt go wrong....earths been doing it 4ever.

 

We have 2 tanks in the house right now...

14g (wife)
8g (mine)

14g - get's 1gallon changed every other day
8g - get's about half a gallon changed every other day

This schedule helps reduce on general tank stress and gives you a better quality of water stats with less established tanks. As time goes on, I'll reduce my water changes to every 4 days and make that my regular water change schedule.

 

I do 15gallons every 2 weeks on my 100gal system.

Seems to do the trick. But overall, i believe in the every 2 week system. Fewer larger water changes help get rid of more nitrates than smaller more frequent water changes. There shouldn't be too much stress on the tank's inhabitants if you keep the change up water consistent in salinity/temp as the display tank's.

 

ive never done a water change and my sps's are doing just fine. but if you were to do them, multiple small amounts has a more stable affect than one big one.

 

Same here.