Poly beads for grow beds??

[anniefish]

Hi all,

Just having a think about media for grow beds - what are your thoughts on poly beads? I was thinking the ones used for bean bags, I know the biggest problem would be the float factor, but they'd be really easy to use:D, save a lot of bad backs, just don't know if they would leach baddies into the system?

Or how about the 'peanuts' used for packing delicate items. I work in an organic shop and they regularly receive goods packed in mountains of the stuff. I'm not sure if they dissolve in water, will try some. They should be 'healthy' if they are used with organic products I think.

Ann

[GaryD]

Hi Ann,

I've heard of people using polystyrene beads as bio-filter media but I doubt that they'd be suitable for grow bed media because:

they float
they blow around in the wind
they wouldn't successfully anchor plant roots
they may cause blockagesGary

[anniefish]

Hi Gary,
Didn't think of the wind and they would get blocked. Oh well, back to the drawing board:D
Ann

[jack@badflas]

I use permabeads for particulate filtration and was considering using them for a growbed, but they would clog up too easily. Permabeads don't float and are used to replace sand in sand filters, but unless you can back-wash them, they would be no good for a grow-bed. They are also VERY expensive compared to gravel.

[echidna]

150-200 mm of poly beads with a 100-150 mm layer of hydroton or gravel might work. You could also think about a layer of shadecloth in between if not growing deep rooted plants.

[anniefish]

Thanks Jack and Echidna,


Good ideas Echidna, will keep thinking on it.

Ann

[Hamish]

WHen I was a youngster (about 7y/o) I started a little business cutting up waste timber offcuts from my fathers wooden ladder factory and selling it as kindling at the local service stations.

I can see you all rolling your eyes and nodding off as I enter another of my stories....

Anyway - there is a reason for telling you this.

I use to pack the kindling wood in used bags from a local plastics factory. THe bags originally contained hard plastic pellets that they melt down to form plastic products.

There were sometimes a few left in the bottom of the bag - and from memory they were about 5mm in diameter.

I am wondering if these could be used as a grow bed media?

They were reasonably dense so I am not sure if they would float or sink. Im pretty sure they would sink - atleast if used in a large quantity in a grow bed.

And indeed I have no idea of the price the raw material would be. Anyone out there in the plastics business?

[GaryD]

Hi Hamish,

I must confess that a similar thought had occurred to me some time back.

I visited a plastics factory in Bundaberg to buy a 200 litre tank to be used as a swirl filter. I had intended to ask the folks there if I could have some polyethylene beads but I was in a hurry and I forgot about it.

If they sink they'd probably be good. Even if they float, they could be used in continuous flow systems. In either case, they'd be good for bio-filter media.

Gary

[Outbackozzie]

I wouldnt mind knowing the cost and if they float or not.

[GaryD]

Hi,

I managed to contact a supplier of polyethylene beads.....Price Plastics at Caboolture (Phone (07) 5499 1111).....and here's what I learned:

The beads are opaque white and they are 2 - 3mm in diameter.
They float (0.938 density)
They come in 25kg bags (equal to about 30 litres in volume).
They cost $2.30kgI'm going to buy some to trial a filter design that I've been working on. Because they float their use as growing media would be limited to continuous flow systems.

Gary

[GaryD]

Hi,

I managed to contact a supplier of polyethylene beads.....Price Plastics at Caboolture (Phone (07) 5499 1111).....and here's what I learned:

The beads are opaque white and they are 2 - 3mm in diameter.
They float (0.938 density)
They come in 25kg bags (equal to about 30 litres in volume).
They cost $2.30kgI'm going to buy some to trial a filter design that I've been working on. Because they float their use as growing media would be limited to continuous flow systems.

Gary

[Outbackozzie]

They'd be smooth wouldnt they? Not much bacteria surface?

[GaryD]

Hi OBO,

I believe that they are smooth but, given their size, they'll still provide plenty of surface area for the bio-film to which the bacteria attach.

I'm keen to trial them in a bead filter. I want to devise a means of easily removing fish solids (I'm over washing out chunks of dacron every day) and, from what I've researched, I should be able to drain the bead filter daily......and remove most of the fish solids.

Gary

[anniefish]

HI Gary,

I found an interesting clarifier on page 5 of this site, http://www.aces.edu/dept/fisheries/aquaculture/documents/309884-SRAC454.pdf

I'm sure you have come across it already. Do you think a smaller version might be useful?

The beads sound interesting, keep us in touch with how they go.

Ann

[Hamish]

Hi Gary - if there were enough beads wouldnt they be less likely to float? I notice that a few clay balls will float - but as soon as you increase the quantity and depth they quickly stop floating.

One concern is that the opaque nature of them might allow light to penetrate and grow algae.

[Outbackozzie]

The clay beads get waterlogged H, thats why they stop floating. I dont think the plsatic will...

[Hamish]

Yes - however they do not get waterlogged right away. There is some effect that happens when a lot of media is put into a container then flooded with water that seems to stop it floating. Perhaps it is friction on the sides of the container - or combined weight - im no scientist as you can see...

[GaryD]

Hi Hamish,



Hi Gary - if there were enough beads wouldnt they be less likely to float?

If the water level in a container full of floating beads is sufficient to water plants (within an inch or two of the surface), it's also enough to float the beads. If you plant into floating beads (or floating clay pebbles), the plants will, over a few flood and drain cycles, gradually sink to the bottom of the bed.

I've been flooding my new clay pebbles for the past three days and they are only just showing signs of becoming waterlogged. The amount of time that it took to soak the pebbles would probably have been less if I'd filled the grow beds right up. As it stands at the moment, I'm a few bags short in each bed.


Gary

[Hamish]

Hi Hamish,
If you plant into floating beads (or floating clay pebbles), the plants will, over a few flood and drain cycles, gradually sink to the bottom of the bed.Gary
Hahahaha - quick sand for plants!

[Ravnis]

I have seen in the garden centers here reground tire chunks sold as landscape mulch. These appear to be from factory defects and not used tires that would have who knows what on them. Hard rubber would not float and it might be a alternative to gravel. I can tell by looking that they are not used tires because they are brown instead of black from having carbon black powder added to them. I don't know if this is available there in Australia. My main concern with polyetheylene beads as grow media is it blows easily and doesnt breakdown. Then birds and animals might eat it and have it stick in intestines. When I worked in plastics, the rats that chewed into the bags did not live long afterwards. We also had to be careful of spills or the EPA would be on us big time. I think I would save the pellets for filter media like Jack showed instead. MY 2 cents.