Backyard Aquaponics
A place to discuss aquaponics

Hi guys, I have been seriously thinking about this over the last few days. My idea was to get a brainstorm, estimate of the feasability of producing expanded clay beads/pellets as growing medium... I have access to clay and a kiln... my dads a potter. I have been thinking of a few ways of easily and efficiently pelletize a mixture of clay, sand and organic materials such as wood chips or coffee grounds. This organic matter will burn off in the kiln leaving the pellets pourous, thus increasing the surface area. It would also cut the cost, weight and restriction of water flow. It will also, theoretically be cleaner than gravels, clay won't crush as easy as other mediums, and depending on the organic particals would only have a bit of ash. I have made fake coral using this method and put the pieces straight from the kiln into my fish tank.

Now, the way this is done commercially is through the use of a pin mixer, basically a large diametre shallow cement mixer with sprayers to slowly add water or similar bonding agent to the mix. My first idea was to use a cement mixer to run a few tests with a sprinkler on a stand.

Somethings I need to detirmine, is there a market for it? Is there a product like it? ... and how much does it cost to buy/transport? How does it compare to the quality/cost/labour intensiveness of gravel and more favoured media?

Sounds like a great idea. Machines to help make them is good! (reading the title i thought you would be making them one at a time by hand, for a long long time)

Sounds simmilar technique to the way stars for firework shells are made.

could you roll clay into long skinny ropes and cut them up into pieces?

Are expanded clay balls not injected with high temp steam to "expand" (make them porus) ? But i like the idea of incorporating organic material that will burn off, both creating voids, and the escaping steam / smoke will link these voids to the exterior of the ball.

Make a test run manually!

QUOTE: "reading the title i thought you would be making them one at a time by hand, for a long long time"

It might be good therapy, "I have an Aquaponics system, and I have a problem" by the second bucket I might get it out of my system. I will need to find a feasible and effective way of making them, with little or no labour besides taking them out and into the kilns.

By what dad reckons a cement mixer may be able to make 12-15 L of pellets at a time (depending on the mixer). Then they have to be spread out, dried then fired. In small batches it may still take a while.

QUOTE "could you roll clay into long skinny ropes and cut them up into pieces?"

I have thought of this option, using the extruders at Dads work. It is too labour intensive, unless I can find a way to automate it. I made small ceramic filter beads using this method, but take too long for large quantities.

QUOTE "Are expanded clay balls not injected with high temp steam to "expand"..."

That is another way of doing it but not for the size and number of pellets I would need. Another way I have looked at is a particular clay that expands like popcorn, but it is far too brittle for this application.

My most recent thought was to make a mould like a 'chocolate bar' and make clay sheets which can be broken into squares once fired... but again too labour intensive...

At a spot i was at last week, they were making small batches of fish pellets with a pasta maker. They put the mixture into a hopper or something, and it was extruded and then a rotating blade chopped them off into the pellet shape. Just an idea

Or if you make test batches in the cement mixer, and they are a success, you could upgrade to a cement truck....then you can tip them strait into the kiln (but then i pin mixer sounds more professional)

Is the aim to get the finished product to be simmilar to pumice in its porusness, lightness, etc? If so that would have HUGE surface area

There may well be a market for it.....but I'd do your homework very carefully. Yes, there is a product like it....it's called Light Expanded Clay Aggregate (LECA) and it's purchased from hydroponic suppliers. It costs between $35.00 and $50.00 per 50kg bag.

It's much lighter than gravel and far less labour intensive to handle. It does, however, have a shorter lifespan than gravel (in hydroponic use anyway)

Sounds like something to do when we have nothing else to do.
Had to say it..
Figure you need a light base material.. like pumice
aerated.
Anyone got any volcanos near them.

what if you mix this with a terecotta clay?

hmmm c1, could we dig one, get it to make the pumice, and use it to heat our water?

YEAH!! good idea Daniel.
I do remember from when in FNQLD all the lava tubes.
There must be shirt loads of pumice around somewhere.
Maybe Jaymie would have a clue.
Or another member...

sorry, all I remember from my trip to Undarra was the clay and the ticks!
There is huge basalt flows, but I don't really recall pumice. Sorry!

No idea here either... no one who has been up that way has ever mentioned it, but you can purchase it from landscaping suppliers I have been told...

LOL, i read that as no one who has ever been up that way has come back......... LOL

We got all the pumice here, whole beaches of it.

Any bad press on pumice? other than it floats...