doing daily auto water changes? what % do you change?

TonapahNorth · Nov 27, 2017

how much do you change daily? I’m not asking about whether it should be done or the net reduction of “whatever” contaminants? I just want to know the percentage of total water volume per day and how you reached that number.

For example, I am changing out 19L (about 5g) per day on about a 240g total water volume system. I don’t know how I got this number. I just did it. I’m wondering if this is too much. I’m not complaining. The system is easy to operate as far as water changing. Although, I use a lot of salt, that’s ok too. I’ve seen the articles showing diminishing returns but is 30 days of 5g water changes overkill? I value the simplicity and ease so, again, I don’t care too much about salt use.

Just thought I’d get a sense of how others approach what amount to change daily. Any thought process behind it?

DLHDesign · Nov 27, 2017

I don't do auto-WC (yet), but would be interested to see the results... Can you edit the poll to add a "Don't do AWC" option (or else make the results publicly viewable somehow - though I don't know if that's a forum config or what...).

Fizzicks · Nov 27, 2017

Id like to see the results as well, without having to cast a random vote.

OREGONIC · Nov 27, 2017

Would love to see results too. I have thoght about picking up another DOS to do this.

Randy Holmes-Farley · Nov 27, 2017

I targeted 1% daily.

TonapahNorth · Nov 27, 2017

I edited the poll although there may be other polls that cover the "i don't do auto water changes" answer

@Randy Holmes-Farley - thank you. Your response carries weight with me.

@DLHDesign - the info you seek may be found in other threads/polls

https://www.reef2reef.com/threads/p...-do-you-change-during-wc.331724/#post-4126012
https://www.reef2reef.com/threads/poll-water-change-frequency.331566/

TonapahNorth · Nov 27, 2017

OREGONIC said:
Would love to see results too. I have thoght about picking up another DOS to do this.

This is how I do it and it's simplicity refined. I will never do another tank without it.

Yuki Rihwa · Nov 27, 2017

I don't have experience about auto water change in saltwater but I did use drip water change system in freshwater, so I'm gonna say if you automated water change less than 10% of your total water volume then it's just a waste of time and water even you do that daily IMO.

TonapahNorth · Nov 27, 2017

Yuki Rihwa said:
I don't have experience about auto water change in saltwater but I did use drip water change system in freshwater, so I'm gonna say if you automated water change less than 10% of your total water volume then it's just a waste of time and water even you do that daily IMO.

10% daily? over what period are you talking about? 10% a week is probably on the light side for those who change water.
See https://www.reef2reef.com/threads/p...-do-you-change-during-wc.331724/#post-4126012

Randy Holmes-Farley · Nov 27, 2017

Yuki Rihwa said:
I don't have experience about auto water change in saltwater but I did use drip water change system in freshwater, so I'm gonna say if you automated water change less than 10% of your total water volume then it's just a waste of time and water even you do that daily IMO.

And you base that on what?

It can make a big difference.
I discuss the mathematics and benefits of all typical types of water changes here:

Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-10/rhf/index.php

from it:

Figure 13. An overlay of Figures 3 and 12 to allow comparison of the differences between nitrate depletion using daily and monthly water changes of the same amount changed.

From Figure 3: Nitrate concentration as a function of time when performing water changes of 0% (no changes), 7.5%, 15% and 30% of the total volume each month. In this example, nitrate is present at 100 ppm at the start, and is accumulated at a rate of 0.1 ppm per day when no water is changed. [these are the zig zag lines]

From Figure 12: Nitrate concentration as a function of time when performing daily water changes equivalent to 0% (no changes), 7.5%, 15% and 30% of the total volume each month (in other words, 0%, 0.25%, 0.5% and 1% per day). In this example, nitrate is present at 100 ppm at the start, and is accumulated at a rate of 0.1 ppm per day when no water is changed. [these are the curves]

TonapahNorth · Nov 28, 2017

@Randy Holmes-Farley I don't know if you've done any further research on this, but do the returns diminish significantly as the auto water change (AWC) gets over 30% monthly? Your graph would suggest so but I'd like your thoughts on this. It appears that as time goes on the impact may be lessened. So would perhaps a 2% or more AWC could have a larger impact on depletion over a shorter period? Maybe after a few months the AWC should then be tapered back to something closer to 1%? Does that make sense?

And what percentage is required for a daily water change to get to an "actual" 30% monthly? I am sure I've seen the information that showed me that due to changing water that has been changed before it (however small) would need to be somewhat more than 1% daily but I cannot seem to find it again.

Randy Holmes-Farley · Nov 28, 2017

It's fairly easy to do the math, but what effects you see will depend on what you are trying to accomplish (adding trace elements, removing accumulated undesirables, correcting chloride/sulfate imbalances, supplementing calcium and alkalinity and magnesium, etc.)

In terms of the % changed daily, after 30 days, the following will remove (or add) the same as one water change of the size indicated:

1% --> 26%
1.25% --->31.4%
1.5% --> 36.5%
1.75% ---> 41.1%
2% --> 45.5%
3% ---> 60%
4% ---> 70.6%
5% ---> 78.5%