Aquarium volume pet peeve

Brew12 · Aug 10, 2018

Does anyone else wish tank volumes were listed more accurately? Personally, I feel the way tank volumes are listed is responsible for many reefers overestimating how much water they have in their systems.

For example, I have a "187g" system. It is 60"x30"x24". Take out around 25g for rock and sand and I should have 162g of water, right? Nope, that would be too easy.

My tank is 1/2" glass so the inside isn't 60" it is only 59"X29"x24". And of course, the water doesn't go to the top rim, it stops around 2" shy. I also have 1/2" glass on the bottom so the water fills a space that is 59"x29"x21.5"

It's only a small difference though, right? Um.. not really. It means my tank actually holds 156 gallons, not 187. Subtract the 25g for sand and rock and I'm closer to 131g total volume in the DT. And if your tank is made from 3/4" glass, the problem is even worse!

Does anyone not think the difference between 162g and 131g could cause dosing issues? Maybe for some products it won't matter. I can't help but think this causes a large amount of overdosing issues.

Ok.. rant off. Thanks for listening!

Crabs McJones · Aug 10, 2018

Same with my tank, its listed as a 40G breeder, but when you put in the dimensions it comes out to closer to 44-45 gallons...I realize that 4 or 5 gallons makes probably no difference, but I'm agreeing with you so just run with it

lol

Reeferdood · Aug 10, 2018

Brew12 said:
Does anyone else wish tank volumes were listed more accurately? Personally, I feel the way tank volumes are listed is responsible for many reefers overestimating how much water they have in their systems.

For example, I have a "187g" system. It is 60"x30"x24". Take out around 25g for rock and sand and I should have 162g of water, right? Nope, that would be too easy.

My tank is 1/2" glass so the inside isn't 60" it is only 59"X29"x24". And of course, the water doesn't go to the top rim, it stops around 2" shy. I also have 1/2" glass on the bottom so the water fills a space that is 59"x29"x21.5"

It's only a small difference though, right? Um.. not really. It means my tank actually holds 156 gallons, not 187. Subtract the 25g for sand and rock and I'm closer to 131g total volume in the DT. And if your tank is made from 3/4" glass, the problem is even worse!

Does anyone not think the difference between 162g and 131g could cause dosing issues? Maybe for some products it won't matter. I can't help but think this causes a large amount of overdosing issues.

Ok.. rant off. Thanks for listening!

I could but the displacement from rockwork will be different in all tanks. I think that is one reason most companies want you to lean to the conservative side of dosing their products..
I have no idea on how much water is in my tank..

Adele · Aug 10, 2018

I have a hard enough time just guesstimating the rock volume. It never occurred to consider the glass thickness as well. When I was getting my Alk and Cal to specs with first time dosing I did my volume guestimate, used the BRS calculator based on that number and dosed according. 30 min later the new alk and cal figures were spot on to where I was trying to get +/- the variance, so maybe I got lucky.

Super Fly · Aug 10, 2018

i use this to calculate, very useful
https://nualgiaquarium.com/calculate-your-tanks-water-volume/#gf_14

andrewkw · Aug 10, 2018

Another potential problem is some products may account for this, ie their dose for a 187 gallon tank is really for 162. I have seen some products say take account rock and sand but never for glass thickness.

Billdogg · Aug 10, 2018

I have a "120" DT with a 40b sump. For dosing purposes I just go with 120g, figuring that the 40b, filled halfway, makes up the difference from the rocks and sand.

ca1ore · Aug 10, 2018

I had a recent thread on this very topic. There are actually a few manufactures that list tanks based on true water volume - in other words measuring ID rather than OD. My current tank, 96x36x30 would usually be claimed as a 450, but it actually holds about 400 .... before any rock or sand displacement.

That 'over claiming' volume results in corresponding dosing problems depends, I suppose, on whether you think that there's any real precision to additive dosing recommendations. I'm a card-carrying cynic, so you can guess what I think .....

Art2249 · Aug 10, 2018

My system holds 160, based on the amount of salt mix used when I first filled it.

saltyfilmfolks · Aug 10, 2018

I just like tanks that are pretty. And I like Rims.

I took Randy’s advice and and made a very rough est if volume , lowered the calculated dose and ran the tank for two months , (to include wc in the calculation) slowly bringing up the dose till I hit the right amount.

I know the scales but also play by ear.

Pntbll687 · Aug 10, 2018

I'm actually going to side with the manufacturers on this one. It's probably an industry standard to calculate using the outside dimensions.

I don't see anyone complaining about the 2x4's and any other lumber they are using to build a stand. Lumber dimensions are almost NEVER right, I believe a 2x4 is actually 1.75 x 3.75 or somewhere in that ball park.

Katrina71 · Aug 10, 2018

Try reefing in an 8 gallon AIO.

KrisReef · Aug 10, 2018

This phenomena also arises frequently in resumes and personal ads.

Art2249 · Aug 10, 2018

Pntbll687 said:
I'm actually going to side with the manufacturers on this one. It's probably an industry standard to calculate using the outside dimensions.

I don't see anyone complaining about the 2x4's and any other lumber they are using to build a stand. Lumber dimensions are almost NEVER right, I believe a 2x4 is actually 1.75 x 3.75 or somewhere in that ball park.

But when you buy a 25 gallon tank that actually holds only 18 gallons, thats a little more than just going by outside dimensions. My advice is to calculate the volume yourself based on the dimensions given.

gcarroll · Aug 10, 2018

Mods, please move the following threar out of the "Large Aquariums 180+" forum due to miscalculation!

https://www.reef2reef.com/threads/brews-187g-slice-of-the-ocean.334401/

ca1ore · Aug 10, 2018

gcarroll said:
Mods, please move the following threar out of the "Large Aquariums 180+" forum due to miscalculation!
https://www.reef2reef.com/threads/brews-187g-slice-of-the-ocean.334401/

Well played sir ....

gcarroll · Aug 10, 2018

ca1ore said:
Well played sir ....

That will make @Brew12 appreciate having a 180+ gallon tank. Thread on page 3 in an hour or two.

KStatefan · Aug 10, 2018

Pntbll687 said:
I'm actually going to side with the manufacturers on this one. It's probably an industry standard to calculate using the outside dimensions.

I don't see anyone complaining about the 2x4's and any other lumber they are using to build a stand. Lumber dimensions are almost NEVER right, I believe a 2x4 is actually 1.75 x 3.75 or somewhere in that ball park.

People do complain about lumber sizes. Home Depot and Menards have been sued for not labeling actual lumber sizes.

saltyhog · Aug 10, 2018

I agree @Brew12 !

My tank (Deep Sea Aquatics) is listed as a 155 gal...72x24x21 but actual inside dimensions are 71x 22.75x 20 of height if you discount the empty space at the top. My sump is 42x18x18. By dosing and checking the change vs the BRS dosing calculator I've guessed my total water volume at right at 150 gallons. At least that seems to work for dosing the big 3.

mcarroll · Aug 10, 2018

Brew12 said:
Does anyone else wish tank volumes were listed more accurately? Personally, I feel the way tank volumes are listed is responsible for many reefers overestimating how much water they have in their systems.

For example, I have a "187g" system. It is 60"x30"x24". Take out around 25g for rock and sand and I should have 162g of water, right? Nope, that would be too easy.

My tank is 1/2" glass so the inside isn't 60" it is only 59"X29"x24". And of course, the water doesn't go to the top rim, it stops around 2" shy. I also have 1/2" glass on the bottom so the water fills a space that is 59"x29"x21.5"

It's only a small difference though, right? Um.. not really. It means my tank actually holds 156 gallons, not 187. Subtract the 25g for sand and rock and I'm closer to 131g total volume in the DT. And if your tank is made from 3/4" glass, the problem is even worse!

Does anyone not think the difference between 162g and 131g could cause dosing issues? Maybe for some products it won't matter. I can't help but think this causes a large amount of overdosing issues.

Ok.. rant off. Thanks for listening!

It is a good point worth thinking about!!

Somewhere along the line I was told that the tank names we're familiar with (e.g. 180 Gallon) are literally product names, not volume measurements.

That's why they're most-correctly written in Capital Letters. "180 Gallon", not "180 gallon".

Yes the name and number are close, but as you found, only sorta close.

My "37 Gallon" is 36x12x19"T....which is 35.5 gallons. (Even smaller, for interior!)

If I count actual exterior dimensions for height and width, but not thickness, I get very close to 37 gallons:
(36.5*12*19.75)/231=37.5

(Actual maximum exterior dimensions are 36.5 x 12.5 x 19.75"T.)

I don't know what kind of scheme that is, or if it's consistent across any other models.

I also don't know why this doesn't seem to matter in dosing or other areas more than it does, but I can't tell if there's any impact to daily operations from it. I don't recall ever getting snafu'd in dosing or salt mixing, for example.

The main impact seems to be "Hey, I thought I got more gallons per dollar than I did!!"