PDA

View Full Version : Tank volume and dimensions at odds in the brochures



stardotstar
Sat Sep 23, 2006, 03:24 PM
I find it interesting that when I calculate a tank volume by simple mathematics I get a figure that I know must be more than the volume of water that the tank will ultimately contain once features, substrate and other material is subtracted from the level the tank is filled to anyway, but when I read brochures I can't work out if they use a percentage to average this or some other rule of thumb...

ie

(186x50x76)/1000=706.8 but the brochure specs the tank at 540L

and

(156x46x69)/1000=495 but product specs list 370L tank

(123x46x67)/1000=379 but listed at 285L

all these figures are less than 80% of the total physical volume - can anyone tell me what kind of rule is generally applied to this.

Clearly it has something to do with the recommended volume of water associated with equipment like filter flow rates and capacities, heater suitability and tank construction.

My tank is to be 153x46x61 which physically is a standard 5'x1.5'x2' tank at a physical volume of 112.5 gallons or 423L but clearly it will be more like 340L at a 10% rule - I will have a sand substrate - not planted and some simple minimalist driftwood and probably fill to within a couple of cm of the top.

DIY
Sat Sep 23, 2006, 11:48 PM
(186x50x76)/1000=706.8 but the brochure specs the tank at 540L


Are you looking at one of the curved edge tanks like jebo, sunsun or aquaone?

The reason I ask is I was getting caught in the same trap when looking at some of those (I think aqauaone is the one I remember getting wildly different volumes) The "trap" is the quoted dimension includes the hood!

example 6 footer

186x50x59 (76cm less 17cm hood) = 548
If you also allow for a small loss of volume at the 2 front edges due to the curve it gets much closer to the quoted 540l

Another trap we all fall into is outside V inside, as an example I'll use a standard lfs built 4x2x2 (feet) tank in 10mm glass.

outside dimensions in cm's
120x60x60/1000 = 432

inside dimensions, wich is the outside less 10mm on both sides...
118x58x58/1000= 397

Allow a couple of cm's from the very top since we dont run the water height to the point of overflowing and it becomes 380 litres, quite different from the original 432!

stardotstar
Sun Sep 24, 2006, 12:22 AM
Excellent - so let me see:

My 153x46x60 made from 10mm glass and filled to within 2cm of the top yields an inside volume more like

(151x44x57)/1000=379L which is significantly less than the 422 you get with the ODs... Hmmm.,

*Chris*
Sun Sep 24, 2006, 12:30 AM
the sun sun brochures are notorious for quoting the wrong tank volumes and they are out by alot
your best bet is to always do the calculations before you buy the tank because even the LFS get it wrong
EXAI