Hauled my last bucket of saltwater! (Hopefully)

[gus6464]

I'm not sure why you think it is a myth. Using your numbers it would reduce the effectiveness by 10%-20%. I do agree that it isn't a reason to not do daily water changes but if I were setting it up, I would try to take it into consideration.

Well my math was also based on doing the water change in a continuous matter where basically new water goes in at same time old water goes out. If op is doing the water change with all the old water being taken out first and then new water being put in it is no different.

 

[Brew12]

Well my math was also based on doing the water change in a continuous matter where basically new water goes in at same time old water goes out. If op is doing the water change with all the old water being taken out first and then new water being put in it is no different.

That would have a minor impact. The bigger cause is that on day 2 you remove some of the cleaner water added on day 1. On day 3, you remove water added on day 1 and day 2. When I did the calculations on this it gave me a worst case reduction in efficiency of 24% per week. This would be removing a contaminant that was added all at once and was not recurring.
The impact is lessened for the stuff we really care about with water changes like raising Calcium or reducing Nitrates since these are continuously being produced and consumed. That math is above my pay grade but I expect that it still reduces efficiency by around 10%.
In the OP's case, if this keeps you from missing 1 out of every 10 water changes you about break even. I'm not trying to discourage this method. I think it is much better than weekly water changes. Just want to point out that it does have a drawback that needs to be considered.

 

[Waterjockey]

Just an update, with the corrected programming, I let the system run overnight, for the equivalent of 18 water changes. I then timed how long it took me to run just the new water pump to bring the level back to exactly where I started. The "slip rate" between the two pumps was about 8%. Divided by 2 pumps, that is a slip rate of about 4%.....that is, in my book, better than expected for an inexpensive 2 roller pump with about a dozen feet equivalent difference in head pressure between the two.
So, I've adjusted the timing of the new water in pump to run 1 minute 40 seconds longer per cycle than the old water out pump.
Second calibration run has started....I think I should be very very close by the end of the day

 

[NeverlosT]

This is an awesome idea and well done!


I will weigh in though on the changing 1 gallon per day or 20 gallons at once. It is less effective due to dilution (although it will certainly still work). If you have 20ppm of an element in a tank, and change out 50% of the water once in a big shot, replacing the old water with new water that has 0ppm, then your new volume of water will have 10ppm of that element (classic dilution).

However, if you have 20ppm, and you change out 10% of the water, then you dilute that 20ppm by 10% (18ppm now), then you do that again the next day and are down to 16.2ppm, then again 14.58ppm, then again 13.12ppm, then again (11.8ppm). So you changed out the same amount of water and ended up with 12ppm of your pollutant instead of 10ppm.

So like I said, it will work, but it is not the same thing as a big water change. The flip side is though, that it may be BETTER, since even though you are diluting pollutants slightly less effectively, you are also not making any big (sometimes accidental) changes to water parameters all of a sudden (like a 50% water change with water that is 5dKh higher in alkalinity than your tank water).

So in all, its a solid plan!

 

[Waterjockey]

Just a last note on my AWC project.
I changed my method of calibration to actually weighing the water on a scale to get a far more accurate determination of amount pumped, than I could tell by eye.

Using this method, I was able to dial the two pumps to pump within 5 grams of water on each cycle....close enough for me

The new automatic water change system was put into the sump this evening, and will perform it's first water change for me while I eat breakfast tomorrow morning and enjoy watching my creatures start their day as well

Thanks everyone for following along and participating

 

[Waterjockey]

This is an awesome idea and well done!


I will weigh in though on the changing 1 gallon per day or 20 gallons at once. It is less effective due to dilution (although it will certainly still work). If you have 20ppm of an element in a tank, and change out 50% of the water once in a big shot, replacing the old water with new water that has 0ppm, then your new volume of water will have 10ppm of that element (classic dilution).

However, if you have 20ppm, and you change out 10% of the water, then you dilute that 20ppm by 10% (18ppm now), then you do that again the next day and are down to 16.2ppm, then again 14.58ppm, then again 13.12ppm, then again (11.8ppm). So you changed out the same amount of water and ended up with 12ppm of your pollutant instead of 10ppm.

So like I said, it will work, but it is not the same thing as a big water change. The flip side is though, that it may be BETTER, since even though you are diluting pollutants slightly less effectively, you are also not making any big (sometimes accidental) changes to water parameters all of a sudden (like a 50% water change with water that is 5dKh higher in alkalinity than your tank water).

So in all, its a solid plan!

Thanks!
I was reading an article by @Randy Holmes-Farley on water changes http://reefkeeping.com/issues/2005-10/rhf/index.php where he does the math comparing 30% changes per month to 1% a day, and it works out to the equivalent to a single 26% change per month...so it's only slightly less efficient. He also notes it may be less stressful to the inhabitants as well, being less noticeable changes, vs larger parameter swings from larger changes.