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For those people setting up new systems, there are just a few things to keep in mind when choosing media.
Primarily, you want media that won't mess with your pH too much. Things like limestone and marble will tend to keep the pH in a system very high due to their calcium carbonate, normally such medias are to be avoided. Shells might not be quite as bad but I still wouldn't recommend them as media, they keep the pH up around 7.6 which is still higher than most plants really like and causes Iron lock out requiring regular additions of Iron to the system.
There are also some medias that have a very low pH tendency, Diotamite or Maidenwell is an example of this. Using such a media will require careful observation and buffering of pH to avoid crashing the bacteria and having terrible ammonia spike.

So before you buy a truck load of the gravel, you might see about getting a small amount to run some pH tests after letting the media soak in water for a while.

FYI pea gravel usually refers to the size of the gravel, not the kind of rock, around here cheap pea gravel is likely to be limestone. Mostly quartz type river pebbles of 1/2" and smaller size are usually a fairly good choice for gravel media. Granite can also be good as can lava rock of appropriate size.
Be sure to wash your gravel before putting it in.

Perlite is generally not recommended as it can be difficult to contain and vermiculite breaks down easily. Of the manufactured hydroponic medias the expanded clay balls of high quality are the only really recommended by many Aquaponics enthusiasts.

Coco Coir, Peat, Sand, wood chips, leaves, and other such medias are generally thought to hold to much water (keep it to wet for the plants) and may also leach undesirable tannins into the water. If trying to use any of these please do it on a small scale in an experimental set up when you can easily take it offline or remove it from the system if something doesn't go right. I once tried wood chips in a small experimental set up and they turned the water so dark that I could not see the fish.

Please add more tips and tricks about media here.

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my understanding is that there are multiple types of coir and I expect the variations between them could be vast.
I know the texture can vary from anything like dust to fibers to small chunky stuff and even large fibrous chunky stuff. Some things are made more with the outer husk fibers and other stuff is made from the ground up hard shells. Some stuff could be soaked in salt water and need leaching to remove excess salts while other stuff is actually already composted and aged. I expect the chemical qualities probably vary too depending on the material, location, and treatment (composting aging etc.)

In my system, I have actually used peat pellets in my NFT cups for plants like cucumbers that actually like a more acidic situation. Will see if it lets me grow some AP cucs or not (my system has a high pH due to shells mixed into my media.)
I have 2 large raft systems and one barrel system. I plant most of my plants or seeds into coconut fiber. I actually shuck the coconuts from my trees and make it into small strips and then throw it into my chipper shredder. It makes it very fine and some is powery. This I use to plant seeds in. I have started planting the seeds in the peat pellets that you get at Hme Depot. I then wait until the seed germinates and then move it into the net pot. I use mostly 3 inch pots. I surround the peat with the coco fiber and put the pot into the holes in the rafts. The rafts are made of 1 1/2 in styrofoam. I got this at Lowes. I plant my taro in 9 in net pots and wrap the plant with cocofiber. All my plants are just hanging in the water. I do believe that some plants might do better in the gravel with the flood and drain system. I hope to try that some day. I do not find that the coco fiber messes with the pH or any other factor and it is cheap if you have the trees.
I love hydroton but its way to expensive. I use it in my smaller hydroponic systems. For my aquaponic biofilter\grow beds i have quartz pea pebbles which work very nicely. I do cover it with an inch of hydroton or so to keep a drier layer and to allow the roots to breath easier.
Sylvia Bernstein said:
I wanted to re-introduce the topic of using coconut fiber (coir), especially after hearing on the webinar last week that the team at Sweetwater Organics uses it for their aquaponic systems. I know it has a reputation for being on the lower end tolerable pH, and can contain salt if you get it from a non-reputable source. That said, there is a product out now called Cocodan Coir Croutons (http://www.composterconnection.com/site/coco-coir-croutons.html) that looks like it might work...and it is way lighter than gravel or Hydroton. Anyone working with coir? Thoughts?
Possible salt content isn't too much of a problem, and can be rinsed out prior to use...

Low pH is a definite with coir... anything from 4.8-6.4.... and can be really problematical in a system that tends towrd pH 6 anyway...

But the biggest problem is just that it remains too wet for "flood & drain".... IMO...
I have discoverered an inexpensive lightweight medium called Stalite (expanded shale). It's ph neutral, pourous, comes in multiple sizes, grey in color AND local! The only possible con I can see at the moment is that it isn't smooth, so may be a little rough on the hands, but the price is great and figured if I had to I could use gloves. The upside is it is porous, holds water but won't draw water out of plants! exciting.
Michille, would love to know more about the product. Do you have a link for it? Amy

Michelle Silva said:
I have discoverered an inexpensive lightweight medium called Stalite (expanded shale). It's ph neutral, pourous, comes in multiple sizes, grey in color AND local! The only possible con I can see at the moment is that it isn't smooth, so may be a little rough on the hands, but the price is great and figured if I had to I could use gloves. The upside is it is porous, holds water but won't draw water out of plants! exciting.
sorry, I don't have a link for it..maybe you can google it.

Amy D Crawford said:
Michille, would love to know more about the product. Do you have a link for it? Amy

Michelle Silva said:
I have discoverered an inexpensive lightweight medium called Stalite (expanded shale). It's ph neutral, pourous, comes in multiple sizes, grey in color AND local! The only possible con I can see at the moment is that it isn't smooth, so may be a little rough on the hands, but the price is great and figured if I had to I could use gloves. The upside is it is porous, holds water but won't draw water out of plants! exciting.
and this is the site for the horticultural use of stalite
http://www.permatill.com


Zachary Stern said:
http://permatill.com/green-roof.php

Michelle Silva said:
and this is the site for the horticultural use of stalite
http://www.permatill.com


Zachary Stern said:
I wanted to mention that I'm getting the 3/8" size . They said this size is smooth and it may hold water a little better.

Michelle Silva said:
http://permatill.com/green-roof.php

Michelle Silva said:
and this is the site for the horticultural use of stalite
http://www.permatill.com


Zachary Stern said:
That would be around 1400 USD just for hydroton.


You might want to research Utelite (expanded shale) and Stalite (expanded slate). Either of these would have a much greater surface area than gravel and are lighter - cheaper than hydroton. There was some discussion of these media on the BYAP site.

I'm tentatively planning to try Stalite - PH neutral. It will be more expensive than gravel but I want the most surface area I can get in the grow beds and a textured surface greatly increases the surface area. More surface area should equal more bacteria.

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