Backyard Aquaponics
A place to discuss aquaponics

If the consistency was right, then the clay would end up pretty perfect in shape anyway. Getting it to ball shouldn't be hard - getting it to ball at the size you want - I'm not so sure. A play with a cement mixer before committing to anything more compliacted would reveal all.

mortar badly needing water (pretty much sand) will ball into about 5mm-15mm
I think if you're making hydroton, it gets screened afterward, or perhaps beforehand.
maybe we need a dicing machine to get it the right size before you round off the corners?

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I think for a workable one that will seriously expand ANY form of pea gravel or clay it would have to be massive.

shoot, i guess the website hosting this image dont allow direct linking... ahh well.

Looks a little blurry. If we are only talking small amounts then the unit does not have to be large as long as the clay can enter and be removed. Even a small bucket forge with some test clay balls and time how long it takes them to pop. If they stick together it would not take a lot to separate them.

Here's a media idea to shoot holes in. Autoclaved Aerated Concrete AAC aka Hebel blocks or panels are given away free when broken. Break them up into smaller pieces (use a sledge and vent your spleen), toss the broken bits into a cement mixer and rotate until the edges are rounded, place in grow beds. Use screens to get the desired size of pebbles.

It's concrete so should have a pH buffering effect, also has lots of holes so good for water/bacteria holding.

Just have to check if it contains anything else. Eg lime.

I reckon there would be to much lime in them

C1 would know... definitely would not advocate standard concrete.

And there in may lie a problem.... it may well drag pH to 8.0-8.5.....

But we have the technology. Will do before and after pH test on jar of distilled water with aac placed in it and report back. Not sure how long to leave it, but a week should do for leaching to occur. Mind you the bacteria in an active system would excrete/exude acidity which may speed up leaching, but then this would be buffered by the lime in the aac.

If anyone can work out how to do it sensibly (a hammer takes a bit of time) crushed tumbled brick would seem to make a good media. It is denser than hydroton but still holds moisture well.
The knock off bits and misfires from brickworks may be a good source.

IMHO Hebel will dissolve quite quickly and the ph will go through the roof (salt will speed this up). Bricks seem like a good idea but you have to go to the effort of crushing and tumbling them.
Gravel is easy, proven to work and cheaper and this is without considering the possible contaminates that are in the clay used to make the bricks. Clay is very common stuff and im sure that different samples would contain different trace amounts of things like heavy metals so with brick you don't know what you are getting.
I have used creek pebble and im having trouble with high ph just because it has maybe 5-10% limestone in the mix and buffers to 7.8 and since this stuff dissolves so easy remedies like acid do nothing. I can't do much to fix this but im sure i would have more luck getting my ph down with gravel than i would with concrete. My 2c

Fishfingers... pH 7.8 is satisfactory.... and may drift slowly as the system matures anyway...

As you say... with the limestone in the media mix... it will probably always buffer to about 7.5-7.8.... it's fine....

You may just have to supplement some of the trace elements ocassionaly... like Iron & Potassium...