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I've been thinking about ways to buy less grow bed material
and keep the media simpler and/or lighter. Do people do layered
designs? That is, how about placing a screen X inches above the
bottom, then a layer of mat/foam media, then topped with a light
material like hydroton or expanded shale?

This way, there would be very high biological surface area in the
mat/foam, and there wouldn't be so much aggregate media to
buy, maintain, etc. The roots could just hang in water-filled space
below the foam.

And, what of irrigation. I'd like to water them under pressure. Is it
reasonable to water a media bed using runners off a poly pipe
like some people do with foam filled towers? It seems I'd just need
enough little feeder lines to achieve the desired GPH.

As for the siphon drain system, I was thinking of having the siphon
or flout in a small separate box connected low in the bed with a
removable grate and/or filter so I just have to clean that periodically
instead of having to remove the siphon/flout.

What do you think? Bad ideas? Are there highly preferred alternatives?

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Layered Grow Bed = Bad idea - gravel is somewhat heavy regardless of what type you choose.  If you want roots hanging in water then the proven methods, NFT, DWC, might be better options.  If you want less media, then pre-filtering with something like a radial flow might work for you.

Regarding the flout idea, see Olomana Gardens, where Glenn uses a stand alone siphon to drain multiple beds simultaneously.  

Maybe. I've actually used hydroton before. It is *very* light. I think 2-3" of it would be no big deal. I've also had roots hanging in air/water before.

The standard bucket ebb n flow systems have two buckets one inside another. Holes are drilled in the bottom of the inside bucket and the drain is in the bottom bucket. Healthy plants almost always grow roots through the holes down into the bottom buckets where it is just water and/or air during a drain phase. I don't see much difference in that and the scenario I am describing except for the layer of foam or filter mat.

Thanks for the tip on Olomana Gardens, I'll definitely check it out.

I put lava rock in the bottom half of my beds and hydroton on top. Both are light and provide good surface area. Your idea of putting a screen between them has merit. That would allow roots to travel and keep the media separated so you won't be pulling up the lava rock when you pull plants. I do sort through the lava rock and use the smaller pieces.

So, I guess you aren't having PH stability problems with the lava rock?

I like that idea. I've read that some plants can pull minerals from lava rock that they need. And, you give me another idea. Maybe I shouldn't leave my beds empty to the bottom. I could go 2-3" hydroton for the dry layer, foam, screen, air, then lava rock in the bottom so bacteria would have a place to flourish and break down any solids that make it through the foam.

Really, I'm just trying to figure out how I can deal less with heavy media that has to be cleaned by using the high BSA foam. If people can grow tower plants entirely in foam, there must be a way to get some of the same advantages in a bed. I always hated cleaning the hydroton in the old bucket ebb 'n' flow system I used to run. If I can minimize this in some reasonable way and still have enough bacterial decomposition, oxygen, and water filtering, then I'm all for it!

Thanks :)

Toss in some red wiggler worms. Thy love fish poop and thrive in grow beds. They produce the best natural fertilizer for plants. They grow so well in GBs that I've stopped my regular worm bins. I don't have any issues with too many solids. After the swirl filter I have started using a clear plastic nut jar (planters or similar) under the water feed to the GBs with poly fiber in them to add some finer filtration. Never have to clean beds so far.

It is funny you mention the wigglers, we just started our first compost bin with them last week. What is your drain cycle? Grow beds seem awfully wet and low in aeration for worms. Then again, I have read they can absorb oxygen from water. Is that how it works, highly aerated water keeps the worms from suffocating?

Exactly. The worms grow faster in the media beds. If for some reason they don't like a lot of water they will live primarily in the upper level of the media.  I actually put the poly fiber from the nut jars on top of the media after it becomes plugged and the worms clean it out and I reuse it.

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