Ahh! I got it. There is really no way to determine the water volume displaced by the sand and rocks, if I had a 350 gal tank and a 100 gal sump I would guess with about 50 percent rock etc, net the rocks we are best to dose aminos etc at the 350 gal figure?
www.hamzasreef.com
Wow, that’s so helpful. Thank you. Do you want to lower it by a certain amount? In the example starting point, lowering from 35 to say 33 is enough?There is a way to calculate this, and it requires you to add RODI water to your system to dilute the salinity. Basically you measure your starting salinity, say 35ppt, then add RODI to change that number to obtain the end result. You plug those into this calculator and it calculates your overall system volume. The last line is important: "keep in mind that too large of a drop in salinity will have a detrimental effect on your tank inhabitants"
System Volume Calculator
Aquarium calculator; Calculate the estimated system water volume of an aquarium using a controlled salinity change.
Agree. Thanks for the input. Extremely helpful. I am trying to figure values for supplement dosing, so don’t need to be perfect, just closer than estimating.TLDR answer: In your example, dose your additive to a level below what you suspect the volume is to be safe. Raise dosage over time if you can measure the additive based on testing (ICP or other).
Longer answer: If it were me, I would do my best to protect the health of my system and avoid as much of a change as possible. If you have a digital salinity pen, this would likely be the best method. Take a base measurement, then add enough RODI to decrease salinity that can be measured. So if the salinity pen measures starting salinity at 35ppt, add enough RODI until the pen reads 34.5ppt. Plug those values into the calculator and the approximate volume is shown. I entered this example below, 35ppt starting, 34.5ppt after adding RODI, 2 gallons of RODI, pen measures in 0.1 units of measure. The calculation is that this is a 138 gallon system.
As the tool states in the fine print, a larger water sample is better to ensure an accurate calculation. But who is going to add that much RODI and risk the health of their system? Not me!
