Backyard Aquaponics
A place to discuss aquaponics

156m2 per gram

Does anyone know what a gram of sand looks like. Its not much. For it to have a surface area of 156m2 seems incredible.

Thats less than a teaspoon of sand has a surface area of around 12.5m x 12.5m.

Not saying that its wrong just seems incredible.

I once looked at the maths involved in calculating surface areas but I gave it up because its only an approximation anyway and I had good reasons for studying biology rather than maths (I woosed out).

stuart, it has to do with the particle size. picute a gram of sand in a fused block, it would have a surface area of the 6 sides added. now work out the surface area of each grain of sand and multiply it by the number of grains in one gram hence the incredible surface area.

BUT it has to be fluidized to work. at a certain vertical water flow rate the sand becomes fluid and behaves like a liquid, each grain of sand is suspended. They are indeed the holy grail of bioflter surface area in the aquarium game. they also tend to pulverise any solid waste due to the very abrasive nature of sand.

so a double advantage for AP?

yes and no, i don't think the solids are an issue with a good gravel bed, and i'd prefer trapped solids to silt. which is what we'd end up with becasue we're not running any mechanical micron filters.

Went looking for the scales to weigh out a gram to take a photo, but they seemed to have gone walkabout.........

But it is rediculously high, and im guessing its prob the finest sand possible to use in fluidbed sand filters....

I can imagine it in my head, a gram cube of sand, "silce it" into slices a particle thick from left to right, and you get tons of slices, each slice with a relatively small surface area on each side, but a relatively small surface area timsed by a couple of hundred (or thousand) adds up.......Then slice the cube from front to back.....and then top to bottom.....and i can imagine that it could have a surface area of 156m2

sand sure trumps our lungs, with its surface area the size of a tennis court (havent checked that, but was told that in biology...)

Doh!!! i took too long typing..

sorry dan, i'm stealing your thunder!

Thats why I'm amazed. Consider the size of alveloi, around .1mm, and when their are about 300 million in a set of lungs weighing x Kg for a surface area of about 70-90m2.

By definition the finest sand has a particle size greater than 0.0625mm. A forty percent reduction in particle size (.06 compared with .1) is going to create a surface area massively greater than 40% by volume.

However if a set of lungs weighs 500g (1kg ?) and has a surface area of 60m2 then that is a surface area of .12m2/g. That means tha the sand has a surface area three orders of magnitude greater than a mammalian lung.

One of the other reasons why I gave up trying to calculate surface areas of mediums was because it was just so much easier to rely on the 2:1 [s]rule[/s] guideline instead.

the 2:1 is really the point, its not JUST bio-media, i'm sure that even 1:1 systems kill that, its the planting space and solids filtration also.

Don't forget that some sand particles under the 'scope are not cube, but irregular shapes, adding again to the individual particle surface area.

im happy to share


Yep, im sure not many sand particles are cubes good for us


yep, hence why i am gonna use a fbsf as will have lots of planting space, but not much gravel and hence not much room for bacteria colinisation, and i plan on stocking the water with a high biomass fish

yep, sand is pretty rough and uneven
http://www.almadenelementary.org/home/S ... index.html

Im not sure how accurate the surface area to volume ratio is for sand (because it does sound rediculously high), but there is no denying it that its one of the highest for a bio meda

This page
Surface Area
calculates that the surface area of coarse to very fine sand is between 11 and 454 cm square per gram

interesting, i guess this helps highlight the discussion on misinformation in another thread

Speaking of bio filters,I would like some opinions on using UV light filters to keep algae buildup down!
Sorry BK for intruding but were still on topic. Ive been offered an 18 watt inline unit on loan to clean up my fish tank (9000 litres) .
thank you all for any information forthcoming.
colin