Media

[TCLynx]

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.

[TCLynx]

We have washed some 1/2" Stalite too.  I'm going to venture to say that we will probably choose 1/2" stalite over 1/2" brown River rock when we have the choice.  Both take a good amount of washing.  We use the square water plant baskets to swish the media in a couple bins of water.  If you place the bins of water up at a comfortable working height it isn't too bad.

I think the 3/4" stuff would be great if I could get it.

[Bob Campbell]

It seems like tomatoes or squash would create quite a large and heavy ball of roots tightly bound to the growing media. 

I have not seen any discussion of this so I'm wondering how this is dealt with.

[George]

My system is young but most roots have come up with the plants I've pulled, although I haven't grown either of those plants yet.  The gravel must then be the shaken and/or plucked out of the root ball.  Some roots will surely be left in the gravel and I've read that some people go to the trouble of getting them out but I don't think it's necessary, especially if you have earthworms in the gravel.  Eventually they break down. 

Bob Campbell said:

It seems like tomatoes or squash would create quite a large and heavy ball of roots tightly bound to the growing media. 

I have not seen any discussion of this so I'm wondering how this is dealt with.

[TCLynx]

Roots will break down in the gravel and be eaten by worms and bacteria.

Now that said, I have encountered a few plants that can become beasts and clog a huge grow bed with root mass in a single season. 

Beware the mint, it can take over a grow bed and completely fill the bed with root mass and choke other plants out.  Contain it in it's own small grow bed that will be easier for you to dump and re-fill when it becomes necessary.

The banana completely clogged up a 100 gallon stock tank.  Beware the banana beast.  They are big plants and trying to remove a large one from a grow bed may require heavy equipment.

Lufa, I had a lufa vine completely fill a 100 gallon stock tank with root mass this past summer.  Luckily after cutting off the vine, the roots are breaking down nicely and new plants are growing in the beds.

I've never experience the above problems with tomatoes but my grow beds are large, if your grow beds are small or shallow you may experience more trouble with toms.  Corn produces lots of roots and when growing corn in the grow beds I needed to check the drains and clean out roots on a regular basis.

Now Squash or pumpkin,  I haven't grown those in AP but the Lufa is a related plant so I will suspect that a huge pumpkin vine might really fill a bed with roots but I don't have much experience there other than to say the lufa vine roots are breaking down nicely so I'm not too worried about it.

[Bob Campbell]

Sounds like roots can become a problem.  I'm thinking it might be best to grow plants with aggressive roots in 1 gallon pots placed in an open ebb & flow tub

[TCLynx]

That would be a way to keep a handle on Mint.

Just beware the open water between pots will tend to grow algae and won't filter system water very well.

[Michael Welber]

Have any of you tried pineapples in media? Are their roots a problem? 

[TCLynx]

I expect pineapples will grow fine in a system if they are planted relatively high (not constantly soaked) and occasionally get a drink in their tops.  Pineapples have minimal root systems down in the ground since they are bromeliads (sp?) and their roots are actually between their leaves and they collect moisture and nutrients from the water that trickles down between their leaves.

[Michael Welber]

Thanks for the info. I thought I remembered that Sahib had pineapples growing but not sure. The Hawaiians have a neat trick of putting dissolved lamp carbons in the middle of the flower to promote rapid flower development. I tried it and it worked beautifully. I'm going to experiment with a pineapple and see how it does. 

[Ryan Chatterson]

Ethylene production triggers flowering in pineapples so another common trick is to just slice up an apple and toss a few pieces into the center of the pineapple plant. I used to have a problem getting mine (25+) to flower at the same time or some would flower and some wouldnt. Now I get 24-25 flowering at the same time. Works great!

Ive grown them in rafts and media beds, just make sure the crown doesnt get too wet and they do great. Looong term crop though :)

[rick kennerly]

Expanded Shale - I'm getting a truck load of expanded shale delivered to my beeyard later in the month, 3/4 inch.  It seems nobody uses 1/2 inch in this area, which is the size I'd prefer.   What I'm getting is actually part of a shipment for an industrial stormwater drainage project.  Turns out, even though this is a major port, shale isn't delivered here often in anything smaller than rail car loads.  

The smaller horticulture sized shale is too fine, I think.  But the small stuff's hard to get here too. There is only one outfit that uses small stuff around here, and they drive up to the NC plant for 9 yards every two years.  

Anyway, I'll have some to sell in the Virginia Beach area, if you want to give it a try.  

I"m thinking shale base with a hydroton top layer in my grow beds.   

[George]

I'm using 1/2 inch expanded slate because 3/4 wasn't readily available.  Why would you prefer 1/2 inch?

rick kennerly said:

Expanded Shale - I'm getting a truck load of expanded shale delivered to my beeyard later in the month, 3/4 inch.  It seems nobody uses 1/2 inch in this area, which is the size I'd prefer.