Calculating system volume from salt addition

[TCoach]

Anyone familiar with calculating system volumes? I have a 120 gallon system I'm finally getting wet and looking to understand total system volume so I can made decisions on dosing, water changes, etc. as I move foward. I think it should be as follows based on a sheet that came with my salt.

Salinity (PPT)/system gallons = required salt

So in my case, I added a full bucket (11KG) to the system and ended at 20.5 PPT
20.5/<system liters>=11000g
<system liters>=11000/20.5
<system liters>=536.59
System Gallons=536.59/3.785
System Gallons = 141.8

Is that formula correct?

Thanks for the verification!
-Chris

 

[Randy Holmes-Farley]

No, the mass of salt mix contains a lot of water in the solids. If you wanted to use such a method, you'd have to determine how much a weighed amount of your salt mix bosted the salinity of a known volume of fresh water..

 

[PotatoPig]

Do you know the mass of rocks and sand you added?

If so, and if you have a rock you can remove and test for density, then you can back calculate the volume of rocks.

Measure the interior tank dimensions (the tank volumes are often reported including the glass volume…) and from that calculate the contained volume, subtract out the rock/sand volume, and then you have your water volume.

 

[Reefering1]

You can dose some sodium bicarbonate, test/record the change in dkh, then use calculator to figure out volume of water

 

[Jay Hemdal]

Anyone familiar with calculating system volumes? I have a 120 gallon system I'm finally getting wet and looking to understand total system volume so I can made decisions on dosing, water changes, etc. as I move foward. I think it should be as follows based on a sheet that came with my salt.

Salinity (PPT)/system gallons = required salt

So in my case, I added a full bucket (11KG) to the system and ended at 20.5 PPT
20.5/<system liters>=11000g
<system liters>=11000/20.5
<system liters>=536.59
System Gallons=536.59/3.785
System Gallons = 141.8

Is that formula correct?

Thanks for the verification!
-Chris

One of our fish medics developed some general calculators. As Randy said though, salts vary in their level of hydration and that makes calculations difficult between brands.

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During the course of caring for our fish, we often need to make calculations regarding several recommended treatment options. Most water quality maintenance steps are supported by calculations provided in the "Reef Chemistry by Randy Holmes Farley" forum. Taking it a step further, additional...

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Jay

 

[X-37B]

I just measure inside dims of the tank and sump.
Example:
My 59x30x21.7, listed as a 170 is actualy 135g's at 19" actual depth.
My sump is 48×18×18. I will run ot at 7" so around 25g's.
Total 160g's. For dosing volume I use this number. 10g's off either way is not going to make a difference, imo, or at least has not for me over the years.

 

[Gregg @ ADP]

I’ve always used this wacky method of adding enough salt to 5 gallons of water to get to 1.025, and then just recording how much salt was added. After that, it’s either multiplication or division, depending on one’s goals.

 

[taricha]

I just measure inside dims of the tank and sump.

I tried some other ways, but nothing was more accurate for me than this+ guessing a correction of added rock/sand.

I feel like it shouldn't be that hard for a programmer to whip up something that takes as input 2-3 pics from different angles and measured lengths of sides of the aquarium and estimates water and rock/sand volume for you.
I think it'd be better than my eyeball guess of rock volume.

 

[X-37B]

I tried some other ways, but nothing was more accurate for me than this+ guessing a correction of added rock/sand.

I feel like it shouldn't be that hard for a programmer to whip up something that takes as input 2-3 pics from different angles and measured lengths of sides of the aquarium and estimates water and rock/sand volume for you.
I think it'd be better than my eyeball guess of rock volume.

Yea im sure someone could but I have never seen the need in 30+.
I dont think we need that type of precision, but many would like to know exact volume.

 

[legacy2mj]

Yea im sure someone could but I have never seen the need in 30+.
I dont think we need that type of precision, but many would like to know exact volume.

I think there is a better product or chemical to use to find this value. I’m trying to actually figure out which one to go with. I could use my LFS aqua spin test to get a more accurate reading than my salifert tests. I think the easiest one to do would be nitrate. I believe on the dosage instructions you should have the raw data stating something along the likes of 1ml/100L will raise nitrate by .5…..* I just pulled these numbers out of thin air*

If you get A good ballpark idea of your system volume first that should make it easier in the end. Like my Cade S2 1200 has a system total of 135 gal… I figure with everything in it I’m truly around 115-120.

So if I take a sample of water pre chemical, then follow dosing instructions based on my volume estimate, dose accordingly to raise “X” amount. Get another sample. Have both tested and see the actual difference in amount before and after dose. If your estimation of volume is close, you should see that in the amount nitrate was raised. This will also tell you if you’re overestimating or underestimating….. I’m sure there is a formula you could plug these results in and get a concrete number. I just don’t know it.

I would say this type of accuracy would be beneficial if you were to use the moonshiners method. Since your dosing so many individuals to fill those chemistry gaps. Accuracy would be pretty important I would say.

 

[Randy Holmes-Farley]

I would say this type of accuracy would be beneficial if you were to use the moonshiners method. Since your dosing so many individuals to fill those chemistry gaps. Accuracy would be pretty important I would say.

I'm not convinced that matters much. Any dosing determined by dose/test/dose/test does not need to know the exact volume because you iteratively home in on a dose that keeps the value right, and misunderstandings of the volume will end up looking just like a little bit more or less of consumption.

 

[legacy2mj]

I'm not convinced that matters much. Any dosing determined by dose/test/dose/test does not need to know the exact volume because you iteratively home in on a dose that keeps the value right, and misunderstandings of the volume will end up looking just like a little bit more or less of consumption.

Yes you’re right, that’s how I got to the values dosed daily for my alk, cal and mag. Felt like a couple months of daily testing and tweaking until I got honed in. I guess I’m speaking less to maintaining daily consumption of your big three and more dosing something like vanadium because your system lacks it. This probably relates more to those who are getting ICP tests and aiming to spot fill those trace elements that will not make or break your tank. But supply all the beneficial nutrients your SPS or other coral are not receiving.

 

[Randy Holmes-Farley]

Yes you’re right, that’s how I got to the values dosed daily for my alk, cal and mag. Felt like a couple months of daily testing and tweaking until I got honed in. I guess I’m speaking less to maintaining daily consumption of your big three and more dosing something like vanadium because your system lacks it. This probably relates more to those who are getting ICP tests and aiming to spot fill those trace elements that will not make or break your tank. But supply all the beneficial nutrients your SPS or other coral are not receiving.

IMO, none of the trace elements we dose need to be that precise. We are dosing them into a window between too low to be adequately bioavailable and high enough to be toxic.

IMO, that window is quite wide for most trace elements. For iron, for example the window is many factors of 10.

 

[Snoopy 67]

I have found that with my last 2 tanks, 250 & 100 gallons respectively, with the sand & rock, & a sump running @ about 50%, the water volume is just about the gallon rating of the tank.