Dosing to determine water volume

[Nor'easter Reefer]

So i do not know my water volume, I can guesstimate but I know my accuracy will be incredibly low, and I'd like to know in case I ever have to dose something in my tank in the future, maybe an emergency, maybe just save me to few days of super low doses as I know my tanks fairly accurate approximate water capacity. Curious if there's something you could supplement that has a very accurate, and easy way to test so I could say "I added X grams of Supplement Y and now my Z measures at ____ ppm, so my water volume should be around 150g" or something like that?

 

[Miami Reef]

Sodium bicarbonate. You can measure the alk increase once it mixes in. You can safely increase the alk within 0.5dKH to 1dKH to determine the gallon capacity.

 

[Randy Holmes-Farley Verified Community Expert]

I suspect the value by any such means will not be greatly more accurate than an estimate by eye.

That said, the larger the alk increase used, the more accurate will be the volume calculation.

 

[Miami Reef]

I sometimes use a calculator for manual alkalinity increases, and I determined the my tank was 280 gallons instead of 260 gallons for the alk dosing calculator.

You’re right, it doesn’t make a significant difference.

 

[Nor'easter Reefer]

Sodium bicarbonate. You can measure the alk increase once it mixes in. You can safely increase the alk within 0.5dKH to 1dKH to determine the gallon capacity.

I suspect the value by any such means will not be greatly more accurate than an estimate by eye.

That said, the larger the alk increase used, the more accurate will be the volume calculation.

Well it just so happens i have been thinking of upping my ALK level a little.. hanging around low 8's and want to try to hit 8.5-9 i think. Just as a buffer in case of equipment failure.

That said I wonder if a hobbyist alk test (hanna) is accurate enough to dial in an accurate conversion measurement?

 

[Nor'easter Reefer]

I sometimes use a calculator for manual alkalinity increases, and I determined the my tank was 280 gallons instead of 260 gallons for the alk dosing calculator.

You’re right, it doesn’t make a significant difference.

I should have done what @tbrown did and actually pay attention to how much water I added when I did my tank start up if I want accuracy :face-with-tears-of-joy:

 

[Miami Reef]

That said I wonder if a hobbyist alk test (hanna) is accurate enough to dial in an accurate conversion measurement?

I believe so. It’s close enough for our purpose. As Randy stated, estimating the exact capacity is not critical. :)

 

[Randy Holmes-Farley Verified Community Expert]

In any case, even the water addition way, it’s an imperfect answer to a complicated question since some ways count some or all of the water in sand and rock pores, even though not much additive dissolves into those spaces.

 

[Nor'easter Reefer]

I believe so. It’s close enough for our purpose. As Randy stated, estimating the exact capacity is not critical. :)

I know I'm terrible at rough estimates haha. So my thought was peace of mind that my guesstimate was close.

 

[Tangdora]

I recently did this on my own tank but did it with a reverse mentality. Probably a bit more complex but Instead of adding chemical I measure changes in salinity against top offs. My tank is 328 gallons and I run about another 68 through my sump (hold about 105) . This gives me a potential max volume of 396 that i knew it could not exceed. Now I have about 300 to 400 pounds of live rock in it as well. Since my tank goes through about 5 gallons a day of evaporation, I used a red sea blue bucket of salt which happens to be exactly 5 gallons. For my testing, I filled it every day till it overflowed and then scooped out 1 gallon ish into a smaller pail just so I can transfer it to tank without spelling, but ensure I was still adding exactly 5 gallons consistently

To estimate my volume, I basically use a tropic Marin hydrometer and a temperature probe to take sg level daily. Since it hard to get exact level i took the SG range that the water level was between ie. 1.0251-1.0252…. After that took the current temp. Using and old chart Randy Holmes provided in an article I map that into excel for the temp ranges only that I used and use linear trend (not 100 accurate but delta are so small between values works for estimates) to break it down to .1 decimal ranges for temp and .001 ranges for SG. After ward I used some excel formulas to map my SG and Temps reading to PPT.

After topping off my tan, waited like two hours till my apex salinity probe stabilized and took another temp and reading with the TM. Afte my spread sheet calculated the PPTs of the second reading. I added a formula to calculate the percent changes of parts with respect to knowing that the change was due to 5 additional gallons of RO water was added did it 4 times using high range value test b4 to high Value after , low to low , high to low and low to high (won’t get into the Math unless asked).

After I had 4 different water estimates I then discarded every value I know could never exceed my true tank water only and sump only volume (up to current sump water only). And average the rest.

After about three weeks of test seem to average right around 350 Gallons (P1) on my spread sheet which was roughly around what I was expecting and have been rolling with since.

Dosing does seem to match product expectations when accounting for this value now.

 

[tbrown]

I should have done what @tbrown did and actually pay attention to how much water I added when I did my tank start up if I want accuracy :face-with-tears-of-joy:

I didn't do that silly, too much work... I calculated total volume and then took 75% of that, then dosed what should have been a half dose and checked my math. Both the 135 and 70 came out almost exactly where the 75% put them.

 

[Nor'easter Reefer]

I didn't do that silly, too much work... I calculated total volume and then took 75% of that, then dosed what should have been a half dose and checked my math. Both the 135 and 70 came out almost exactly where the 75% put them.

I took it serious when you told me that :face-with-tears-of-joy: :face-with-tears-of-joy: