Backyard Aquaponics
A place to discuss aquaponics

Greetings,

I've been racking my brain trying to think of a grow medium that fit the characteristics required for aquaponics that will also be rather cheap. In my opinion based on what I've learned those are.

Strongly recommended
-Holds moisture fairly well (but not too well.)
-Porous / bumpy medium both for the roots benefit and the bacteria
-Air gaps between medium for good airflow to the roots
-Doesn't adversely affect PH
-Food safe.

Loosely recommended
-Weight - not a hard requirement but Its nice to have something light.
-Touch & Feel - Nice to have something thats not going to tear into your hands.

So I'd like to be able to build some large grow beds but the cost of the medium is somewhat daunting. Hydroton obviously fits all the requirements but is the most expensive at about $27USD a cubic foot on amazon. If I go with small rock such as gravel I can manage that for about $7.3 per cubic foot. That's cheaper but it will be HEAVY (plus water weight) when I fill up an entire bed made out of wood. So I've been searching for something else that has the properties I'm looking for a cheaper price. I'd really like your input if any of you have found some innovative ideas for grow bed medium on a budget. Thanks for your input!

One Idea I had was cork. It looks like I can get it used for about $24 a cubic foot from 'widgetco'. On the face of it it seems like cork has many of the properties I'm looking for. Anyone ever tried cork in a grow bed? How does it last? How well do you think it will work? Its as cheap as I'd like it to be but it is cheaper than Hydroton.

i don't think it would work, apart from breaking down, it's way to floaty

I think the floating would be an issue too.

I'm not sure how it'd break down though, wine bottles seems to last for quite some time. If you want to have a go, buy a small amount and do a small scale test.

I still think gravel is awesome. Just get a small hand shovel, or a pair of gloves and it's easy to work with. And if you're building a bed, I'd recommend over engineering it anyway. The water is still quite heavy.

You should be able to find Hydroton for $25/50L, or $14.20 a cubic foot. Check out the local "indoor gardening" stores.

Yea, too crumbly after being wet for some time.
The floatiness is also pretty obvious, however after 6 months of soaking it may only float half as much. LOL

I like your line of thinking. I do not think cork will work the way you want, but not for the reasons stated above. Cork bark will eventually saturate and remain neutrally buoyant, and it does not break down very much. I've had two pieces of cork bark waterlogged for years, then dried out in the sun, then waterlogged, then buried underground for a year or so. I just dug the bed back up and the cork bark was still intact.

I think the problems are going to be with root adhesion and, for lack of a better word, friction. The roots are going to worm into every nether and crevasse, and you will be pulling out giant clump clouds of bark every time you harvest. Also the buoyancy will cause the cork to jostle around like a fleet of aquatic bumpercars.

An option I'm strongly considering, especially for the bottom part of the growbeds, is charcoal. You can make a biochar retort from two barrels and produce .5-1 cubic yard of biochar a day (think natural lump charcoal.) It will wick water really well so it is not ideal for a whole solution. charcoal mixed with gravel sounds interesting to me.

I have about 200L of expanded clay right now, and I've looked to find it in the construction industry, but no avail. I've thought of using gravel on the bottom and clay up top where you're working it with your hands.

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Dragon, Neutrally bouyant media is not good, it is basically floating....
the breaking down comes when there are small pieces that rub against each other, your large single pieces you have used may not have broken down, but are the edges still smooth? Rubbing is the problem with cork, rough edges break away easily and this would be a massive problem in AP systems.

I personally wouldnt mix a soft, lightweight media like charcoal with heavy, hard, sharp rocks either, the charcoal will end up crushed, charcoal powder through your whole system, etc.
Try it out, but dont be dissapointed if you get problems.

I was planning to pair the charcoal with expanded shale aggregate. I'm sure it will break down. I still want charcoal in the system to adsorb PVC esters. I made my first batch of biochar today, it went well. But if it will make a huge mess, maybe I will build in a charcoal filter into the system.