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.

[Michael Welber]

Thanks. It's a ways to go but perhaps I can work it out. No truck here...

[Michael Welber]

Love your $ signs smiley. Yeah it's a problem. Thanks. 

David Hart said:

Hi Michael, Yes, you can top off river rock with hydroton.  Even river rock and lava can be expensive here in FL, especially buying it in little bags at the big box stores....

[David Hart]

 I laughed when I saw the smiley with the $ signs too.

After trying to fill 2 small mixing tubs with 'bagged' rocks from the big box store....that's what I saw...$$$...it took about twice as many bags as I 'guessed'

Measure your media bins carefully and think about what TCLynx and I menetioned....you might be able to find some rocks 'some where' cheaper.

Of course it depends on how much you 'actually need'...Maybe even hire a 'handy man/yard man' to pick some up for you. These guys are usually a little 'slow' in the winter time....they might be looking for a way to make a buck or two.

Check 'craigslist'....I sometimes see dump truck drivers offering to make 'runs' when times are slow.

Good luck.

[Michael Welber]

thanks David. Actually "winter" here in the Keys is when it's not slow. However, I have some leads on some local places that have rocks. 

What's the formula for how much I need? I have three 4X3 IBC grow beds and I want to put about 10" of rock in them, and then I'll add 2" of hydroton. So what do you think I would need? Most "rock" places measure in yards, a measure I've never been able to figure out. Bags of stuff comes in liters. It's confusing. 

Thanks again for your help. 

[Vlad Jovanovic]

Mike, just be careful when purchasing lava rock as a lot of the lava rock sold for landscaping/decorative purposes in the U.S was previously used in water/chemical treatment plants...Ask the people at the yard what the lava rock was used for prior to coming to them...Hopefully they'll be able to tell you...

Michael Welber said:

I'm interested in what you say about river rock and lava rock. Because Hydroton is small it takes a lot of it to fill the IBCs and, as you say, it becomes expensive. Home Depot carries both lava rock and a decorative river rock. Would both --either? -- work for the grow beds if I fill the top two inches with hydroton? I don't have easy access here in the Keys to large amounts of either but then I'm only filling three IBC beds. 

[Michael Welber]

Thanks. Good suggestion. I think, based on what you said, that I'll avoid lava rock. People who sell rocks don't always know their origin. 

[David Hart]

Michael, hope this helps....

(10 inches or)  .83 ' x 4 ' x 3 ' x  =9.96 cu ft (per IBC)

9.96 x 3= 29.98 cu ft

 

A cu yard has 27 cu ft.

If I remember.....a ton of river rock averages about 1 1/4 - 1 1/3 cu yards

 

I think those little bags at the box store are .5 cu ft.

So you would need about 60 bags .....

 

Then your looking at hydroton....

(2")   .16' x 3' x 4 '= 1.92 cu ft....for 3 ibc's....5.76 cu ft of hydroton....or 163/164 liters....

 

 

I guarantee my math....to possibly be wrong...

[TCLynx]

David, got the numbers backward on the river rock (it is heavier).  I believe it takes 1.25 ton to make a cubic yard.

The expanded shale or slate in the 1/2" size a ton will make about 1.25-1.3 yards

[David Hart]

My math was good....just my memory is slipping....

Tc is right...I got it backwards, on the ton versues cu ft

[Michael Welber]

You both are amazing. I can't thank you enough! 

[TCLynx]

After handing around 18 tons of the brown river rock, I figure I'm fairly experienced with the stuff.

Just make sure you test any media to make sure you are not putting limestone, marble or shells in as media.  Basically rinse a hand full off and then drop in a glass of vinegar to see if it Dose Fizz or not.  Limestone, marble, shells or coral will Fizz in vinegar and you don't want them in your gravel beds.

[George]

You sure are, much like Tom Sawyer and the fence.  Just kidding.  Beware the 1/2 inch Stalite.  It has a lot of fines, right on down to ground pepper size.  I'm using it but I did a lot of washing and grading.  It's too early for me to recommend for or against it but I believe it will be OK - just a lot of work.  Michael, if you could get some 3/4 inch Stalite trucked down from Miami, that would probably work very well for you.  Good luck.

TCLynx said:

After handing around 18 tons of the brown river rock, I figure I'm fairly experienced with the stuff.