Water Displacement

[Elricsfate]

I am wondering how you guys calculate your water volume for things like dosages, flow rates, and other stuff that requires you to know how much water is in the tank.

A 150g aquarium holds roughly 150g of water. But once you add sand and rock, overflows, etc...you are somewhere less than 150g of water. Do you guys generally just go off 150g, or do you attempt to calculate the actual volume of water in the tank?

 

[Vorog]

Personally I calculated when I added the water to my tank. I have a 75g with 40 breeder sump. My total water volume with sand (100 lbs) rock (90lbs) is 90 gallons. I have always wanted to know if there is a method to measure after the fact. Following to see if anyone has a equation for it.


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[mcgyvr]

For flow rates I just use tank size.. The "range" of acceptable is so large that the difference won't matter..

For dosing you test.. No need to estimate there.. But yes I start with the tank size and adjust as needed..

 

[scooter31707]

Try this link below.

http://reef.diesyst.com/volcalc/volcalc.html

 

[Elricsfate]

Thanks for the input. I appreciate it.

 

[75mixedreef]

I usually say the displacement and sump extra capacity cancel each other out unless your sump is huge or you have a lot less rock than average. Just go with your display tank size. It is close enough for a rough estimate. Testing and observations will let you dial it in from there.

 

[Fish Keeper82]

For dosage I would try to calculate water volume. For flow rates I generally use tank size.
I find the BRS calculators are spot on for dosing( as long as you mixed the right amount of calcium and alkalinity per gallon) come up with an estimate, test your ALK for instance then use BRS calculator to enter water volume, curent ALK, and desired ALK. After dosing wait 10 mins then retest. If your ALK raised the right amount your estimate is good for dosing. If you find higher ALK than you wanted lower estimated gal in the calculator. If you find less ALK than you wanted increased water volume in calculator until you find the right amount.
Remember test kits are just hobby grade so they are not 100 percent acurate plus add in human error to that .So don't get to crazy with adjustments, make slight adjustments.
Example if you had 8 dkH and you wanted 9 dkH after dosing you came up with 8.8 dkH I wouldn't adjust anything until the next time you wanted to dose.

http://www.bulkreefsupply.com/reef-calculator

 

[Fish Keeper82]

You could also raise it half way like to 8.5 dkH then test. Then adjust etc....
Lot of ways to play with it.