How much water is actually in my tank?

[aaron186]

I’m starting to dose my tank and have somewhat of a dumb question. The BRS calculators ask for your total water volume. Do you use the reported volume from your tank manufacturer? I assume that is empty and totally filled and without equipment rocks and sand. I didn’t calculate how much water I actually put in the tank when I filled it. The tank is a Red Sea Reefer 425. Should I just guess there’s about 90 gallons? Curious what you guys do

 

[Timfish]

Well, as I have a fairly good guess of the approxamite weight of the rock used for the aquascaping I subtract that from the weight of the water if there was no aquascaping. But it is just a guess.

 

[BaliReefBox]

Umm how much rock and sand do you have... L X W X H (water level) and sump the same then less 20%..

 

[Reefer Matt]

I’m starting to dose my tank and have somewhat of a dumb question. The BRS calculators ask for your total water volume. Do you use the reported volume from your tank manufacturer? I assume that is empty and totally filled and without equipment rocks and sand. I didn’t calculate how much water I actually put in the tank when I filled it. The tank is a Red Sea Reefer 425. Should I just guess there’s about 90 gallons? Curious what you guys do

It's usually an estimate by subtracting how much water gets displaced by the rock and sand and subtract it from the total tank volume. But if a sump is attached then add that volume back in. It will take a while to tweak the correct dosage, so testing often during the initial dosing period will be beneficial.

 

[EricR]

I take no responsibility for accuracy here but I've seen online calculators that take into account rock displacement based on weight (best estimate) like this one:

Aquarium Volume Calculator

 

[vetteguy53081]

I’m starting to dose my tank and have somewhat of a dumb question. The BRS calculators ask for your total water volume. Do you use the reported volume from your tank manufacturer? I assume that is empty and totally filled and without equipment rocks and sand. I didn’t calculate how much water I actually put in the tank when I filled it. The tank is a Red Sea Reefer 425. Should I just guess there’s about 90 gallons? Curious what you guys do

I go with 85-90% of total volume to allow for rock and other items which reduce total volume.
Example - your tank I count as 82 gallons as I believe its 88g total
A 100g tank would be 90 gallons

 

[flagg37]

It’s fine to estimate.

 

[ca1ore]

Most tank manufacturers materially overstate the volume of their tanks because they use external dimensions rather than internal. So you’re off by 10% before you even begin to try to estimate displacement by rocks and sand. Fortunately it doesn’t really matter as dosing isn’t that precise anyhow.

 

[aaron186]

My tank is 112 total per RS. So would saying 90 gal be accurate? I didn’t weigh my rock either.

 

[1112-425XL]

I have the same tank. 112g with sump. I always dose using 100 as my total. Its just an estimate and keeps my #'s where I want them.