Continuous water change questions

[Toddah]

40 Gallon Cube
20 gallon remote Sump
Skimmer producing great skimate
Mixed reef
Lots of snails mixed group
2 clowns
2 Euphyllia, ricordea a group of about 10, zoes on the sandbed island

I have a 4 year old mixed tank that I have been doing water changes using a dual diaphragm pump but not as a continuous water change.
I recently acquired a DOS pump for my Apex system and now I have very granular control of the volumes that are being exchanged.
I am currently changing 32.7mL around every 15 minutes so around 30 gallons a month (I think) of the approximately 50 gallon capacity.
I am looking for a good balance between healthy water quality and economy of salt costs.
I also have a 4 head dosing pump for dosing additives of what ever I need.
I am going to just run the DOS for a few weeks to let it reach a new equilibrium and see where things end up.
I was dosing Vinegar for a few months and in anticipation of the CWC I have been reducing that dose until I am now off it completely.

I am looking for any advice you can contribute as to anything I should watch out for or if I should be doing less volume on the DOS or more interval in between the cycles of water change.

Thank you in advance for your attention.

 

[Randy Holmes-Farley Verified Community Expert]

I change 1% daily, which is a lot less than you are changing. Nothing typically wrong with changing as much as you do, except cost, as you note.

 

[jonelder68]

I follow Randy and do 1% daily with a DOS QD. As far as the DOS goes I recommend reversing the counter clockwise rotation for the right side/removal head. It makes priming and calibration a real pain. Just run it clockwise same as Left side. You’ll have to change it after setting up default AWC.

I then just check salinity weekly while doing nutrient checks. Confirms everything is working/calibrated fine. Recalibrate DOS every couple months (2-3). So far hasn’t drifted out of calibration and working great!

 

[UmphreakMcGee]

I follow Randy and do 1% daily with a DOS QD. As far as the DOS goes I recommend reversing the counter clockwise rotation for the right side/removal head. It makes priming and calibration a real pain. Just run it clockwise same as Left side. You’ll have to change it after setting up default AWC.

I then just check salinity weekly while doing nutrient checks. Confirms everything is working/calibrated fine. Recalibrate DOS every couple months (2-3). So far hasn’t drifted out of calibration and working great!

Can you go into more info on running clockwise? I’m about to set mine up.

 

[jonelder68]

https://www.reef2reef.com/threads/finally-got-a-dos-for-awc’s-any-tips-or-hints-appreciated.744640/
All in this post and better written than I can do . If have anymore questions after let me know.

 

[siwyJack]

I have run continuous water changes on reef setups for years, and the main thing to get right is consistency over volume. Instead of one large weekly change, breaking it into small, frequent cycles keeps parameters stable and avoids stressing corals or livestock.
The core setup usually revolves around a dedicated drain pump triggered by a level sensor, paired with an add pump that runs only after the drain cycle finishes and the sump stabilizes. Using a flow meter on the add line is non-negotiable for accuracy; without it, you are guessing how much actually enters the system.
Keep the drain and add cycles short and space them out evenly across the day. If you are mixing salt in a buffer tank, make sure the circulation pump runs continuously so the salinity stays uniform before any water moves back to the display. Monitor your sump level closely during the first few weeks; small leaks or evaporation differences will throw off the balance until you dial it in. Once the cycles are predictable, you will notice less skimmer foam variation and more stable calcium and alkalinity.

 

[Randy Holmes-Farley Verified Community Expert]

If you are mixing salt in a buffer tank, make sure the circulation pump runs continuously so the salinity stays uniform before any water moves back to the display.

Salinity would not change in a closed reservoir. No stirring is needed. :)

 

[Randy Holmes-Farley Verified Community Expert]

Using a flow meter on the add line is non-negotiable for accuracy; without it, you are guessing how much actually enters the system.

FWIW, very few people do auto water changes that way. Most people use matched dosing pumps, as I do.

 

[dwest]

I’ve been doing daily 1% AWC for about 8 years now. I used to use Spectrapure liter meter 3’s, now I use a DOS.

 

[jonelder68]

I’ve been doing daily 1% AWC for about 8 years now. I used to use Spectrapure liter meter 3’s, now I use a DOS.

Same! Daily 1% AWC with a DOS pump. Works awesome!

 

[BeanAnimal]

Using a flow meter on the add line is non-negotiable for accuracy; without it, you are guessing how much actually enters the system.

FWIW, very few people do auto water changes that way. Most people use matched dosing pumps, as I do.

I want to add to what Randy mentioned here. The pumps don't even have to be exactly matched. There will be salinity drift, but at a few percent a day, the error between the two pumps has to be rather large for salinity to drift quickly. You may have to make an adjustment every few weeks or months. The adjustment is just dumping in extra saltwater and letting evaporation raise the salinity a bit, or draining some out and letting the ATO make up the difference.

My system is ~125 gallons. I somewhat arbitrarily pump 500 - 1000 mL or so of saltwater in per day. The KH Director does three tests per day, and I have a skimmer. I don't measure how much either removes. The makeup water is just a guess. I am sure it is off by a good bit. If the salinity creeps up over a month or two, I just drain a few gallons from the sump and let the ATO refill it. I have a pump that I can set to do this over a few days. I may adjust the SW doser down a little at the same time. If the salinity drifts low, I just adjust the SW doser up a bit and let the salinity drift back up.

The point is that the two pumps don't need to be exactly matched.

I am not aware of any low volume marine safe flow meters that are accurate enough at reasonable, but maybe there is something out there that fits the bill. What devices are you using?