GaryD

iAVs.info - the Integrated Aqua-Vegeculture System

381 posts in this topic

Hi,

 

The following articles have been added to the iAVs site:

 

While we are getting some comments, we are still largely operating in a vacuum when it comes to giving people what they want.

 

Feel free to express comments or concerns and ask questions.

 

 

Gary

Edited by Gary Donaldson (see edit history)

Share this post


Link to post
Share on other sites

Hi Matt.

 

Two out of three of my sites are belly up at the moment.  My hosting company is transitioning to new servers and there's been an issue with the server that hosts my sites.  It should only be a few hours…..hopefully.

 

Gary

Share this post


Link to post
Share on other sites

The experiment was comparing four sand types, from left to right:

  • Screened sand
  • Mason sand
  • Bank run
  • Salting sand

I had sieve analyses for the screened sand and bank run - both were smaller in size than the iAVS recommendations.  The others didn't have that analysis.

 

I didn't have a specific thing I was testing - just wanted to see how they worked.  What I found was that the sand with smaller particles tended to displace easily and wanted to run to the drain.  The salting sand had larger particles, and was more stable.  I think even the salting sand had a too-high concentration of small particles, though I don't have empirical evidence to that effect.  My impression is that it drained more slowly than it should have. 

 

I'm going to do a test with that sand on a longer bed, but I think I'll keep looking for a sand with fewer small particles.  If I can't find one I guess I'll have them custom-screen me some.  

 

If anyone else finds a source for / name of a type of sand that tends to fit the iAVS specs I'd love to know.  Thanks!

 

Jeremiah

crsublette likes this

Share this post


Link to post
Share on other sites

Hi Jeremiah,

 

Congratulations on your efforts to better understand sand as an aquaponics medium.   While several people have criticised the use of sand, you're the only one (aside from Ravnis) to actually put it to any practical test.

 

When I looked at the photo of your trial bed, my first thought was that none of those sands in the photo was anything like sand as I understood it.......and then I realised that the light (and the photo) was the issue and not the sand.

 

What you're looking for is a coarse sand (graded and washed is best) of the type used for top dressing sports grounds. 

 

Gary

Edited by Gary Donaldson (see edit history)

Share this post


Link to post
Share on other sites

Jeremiah,

 

"Top dressing sand" is a term that is used in Australia to describe a coarse sand that is used to promote good draining and to level the surface on sports fields.

 

At the end of the day, you're looking for a washed and graded (inert) sand of the right particle size.  There will be quarries in your area who understand the terms "washed and graded" and who can provide sand of the right specification.

Gary

Share this post


Link to post
Share on other sites

Gary, with your permission I would like to forward the link to your iAVs site to the agricultural community here in Hawaii, many of whom are themselves running aquaponic and or aquaculture systems.

Share this post


Link to post
Share on other sites

Dr. Benny Ron posted a link to it and bios of Gary and Mark at "The Aquaculture Hub."  FYI.

 

I think I found the sand type and name in the US.  It's called "washed torpedo sand."  It's not perfect, but not bad.

Share this post


Link to post
Share on other sites

Gary, with your permission I would like to forward the link to your iAVs site to the agricultural community here in Hawaii, many of whom are themselves running aquaponic and or aquaculture systems.

 

Feel free, Jim.  We appreciate any assistance to get the word out.  The farmers in Hawaii seem like a progressive bunch.  They seem to grasp any good idea and run with it.  I've been reading about how they've taken to Korean natural farming techniques.

 

Dr. Benny Ron posted a link to it and bios of Gary and Mark at "The Aquaculture Hub."  FYI.

 

I think I found the sand type and name in the US.  It's called "washed torpedo sand."  It's not perfect, but not bad.

 

Jeremiah......I find it difficult to believe someone is not washing and grading sand.......for all sorts of purposes including for use in filters.

 

Gary

Edited by Gary Donaldson (see edit history)

Share this post


Link to post
Share on other sites

In my most recent conversation with Mark, he re-affirmed that the sand that he bought from local quarries was "washed builder's sand".  While it contained some finer material, the material was free of silt and clay - and he confirmed that it was inert through laboratory analysis.

Edited by Gary Donaldson (see edit history)

Share this post


Link to post
Share on other sites

Ok that makes sense.  Thanks Gary.  In my area they call that "washed torpedo sand".  I suspect that washing takes out the silt and clay, though they still have some particles (small percentage) that pass a 100 or 200 size filter.

Share this post


Link to post
Share on other sites

Hi Gary, not sure if I'm missing it, though is there a 'how to set up your own iAVs' section to the website? eg DIY instructions for those that want to try a system?

Share this post


Link to post
Share on other sites

Hi Gary, not sure if I'm missing it, though is there a 'how to set up your own iAVs' section to the website? eg DIY instructions for those that want to try a system?

 

Hi Matt,

 

It's on its way, mate!

 

Gary

Share this post


Link to post
Share on other sites

Timely Gary, It was pretty much what I was thinking of doing.  After several hours of research however, I'm still nowhere as to where to source the sand in WA.   I've found Gingin Quartz:

 

http://quarry.rocla.com.au/resource/Technical%20Data%20Sheet%20Gin%20Gin%20Quartz.pdf

 

it seems to have

92% of particles over 0.15mm

75% over 0.3mm

45% over 0.6mm

25% over 1.18mm

3% over 2.36mm

 

So still seems to be a bit on the 'small' size.  Is Brickies sand too fine as well?  And is pool filter sand too course?

Edited by mattyoga (see edit history)

Share this post


Link to post
Share on other sites

brickies sand normally has a % of clay in it to give it plasticity when worked

 

you are looking for sharp sand and/or washed sand.

 

sharp as in jagged edges on the surface (not rounded edges like river sand) and washed as in washed the clay out. the finer grades are usually beach sand, the coarse stuff can be the screened fines out of a crusher. The reason it is screened to a size is because if you have a gradient of all sizes in there, the smaller ones will fill the gaps between the larger stones and there will be no air gap and the media will be locked together as a single mass.

vkn likes this

Share this post


Link to post
Share on other sites

Thanks - I thought Brickies sand was no good, though the sand selection guide http://iavs.info/commercial/sand-selection-guide/ suggested that brickies sand may be ok and does not have clay.

 

Why are sharp edges desired over round?  I would have thought it would be more prone to compaction and decrease in air void space (will always have a space between spheres) 

 

I can find people selling sharp sand and/or river sand, though they generally don't know the grading on it - that the difficult part finding larger particle size graded sand ( hence my question regarding pool filter sand as this seems to be large grained generally, and can be picked up from pool maintetance co's for free).

 

Kinda of ironic looking for sand in Perth when the whole bloody place is one giant sand pit with very low levels of clay and silt.  Perhaps I should just try my garden sand!

Edited by mattyoga (see edit history)

Share this post


Link to post
Share on other sites

Further thoughts - are there any simple tests that can be done to assess sand samples?  

 

For example

 

1. the soil shake test (soil and water in a jar, shake, then leave to settle gives an indication of clay and silt content, and would give a rough grading of particles.

 

2. acid test to determine stability in acid conditions

 

3. Water hydology test - eg pour 'x' Litres of water through a 'y by z ' cm column of sand and time how long it takes to permeate through

 

4. air pore - see how much water it takes to fill container of sand to the sand level.

 

 

and another question - in the pics  http://iavs.info/wp-content/uploads/2015/04/R411-folio-prints.pdf  what is the purpose of the centre ridge imbetween the toms with nothing planted in it?  Why not just have a wider channel, and/or wider ridges for the toms?

Edited by mattyoga (see edit history)

Share this post


Link to post
Share on other sites

brickies sand normally has a % of clay in it to give it plasticity when worked

 

you are looking for sharp sand and/or washed sand.

 

sharp as in jagged edges on the surface (not rounded edges like river sand) and washed as in washed the clay out. the finer grades are usually beach sand, the coarse stuff can be the screened fines out of a crusher. The reason it is screened to a size is because if you have a gradient of all sizes in there, the smaller ones will fill the gaps between the larger stones and there will be no air gap and the media will be locked together as a single mass.

 

Brickie's sand does often have some clay in it.....which is why brickie's sand technically shouldn't be used for making concrete.  Washed construction sand is what we are looking for.

 

Further thoughts - are there any simple tests that can be done to assess sand samples?  

 

For example

 

1. the soil shake test (soil and water in a jar, shake, then leave to settle gives an indication of clay and silt content, and would give a rough grading of particles.

 

2. acid test to determine stability in acid conditions

 

3. Water hydology test - eg pour 'x' Litres of water through a 'y by z ' cm column of sand and time how long it takes to permeate through

 

4. air pore - see how much water it takes to fill container of sand to the sand level.

 

 

and another question - in the pics  http://iavs.info/wp-content/uploads/2015/04/R411-folio-prints.pdf  what is the purpose of the centre ridge imbetween the toms with nothing planted in it?  Why not just have a wider channel, and/or wider ridges for the toms?

 

I think you've done a good job of identifying the necessary tests.  The "shake" test will do exactly what you've suggested......and so do the others. The acid test is the only one that would require some thinking about......the rest are pretty straightforward.

 

The particular furrow layout and spacing used in the ratio trials sought to:

  • Provide an indicator that the water had reached the right height in the bed.
  • Facilitate water transfer into the sand.  Detritus builds up in the valleys of the furrow.  The extra furrow allows for more lateral space for the water to penetrate the sand.
  • Provide the same spacing between the plants - to ensure that all plants got equal access to light. The spacing in the beds was the same as the spacing between two beds.  This was the main reason for the furrow layout.... bearing in mind that these were scientific comparative trials where everything in the 16 systems (except the specific parameter being tested) had to be identical.

The most important thing is that there should be furrows.....they are essential to the design.  Their precise makeup, however, is up to the operator.

 

Back on sand for a moment.....if you read this article you can see why the sand that is used for golf courses would be suited to our purposes.

Edited by Gary Donaldson (see edit history)

Share this post


Link to post
Share on other sites

Hi,

 

We've recently started to develop a Goods and Services directory on the iAVs site......to help people find the pumps, timers and all of the other items that will be useful for those building a system.

 

Feel free to provide suggestions or ideas for how this can be made better......or more comprehensive.

 

We've also posted an article called......."Dare to Compare?".....in which we compare the iAVs and UVI raft system.

 

Gary

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now