OK Ya'll I need to make a media decision today ...

[Bob Vento]

Morning aqua guys and gals,

I sure could use a push or nudge to make a decision on what media to use in my grow bed. I know that hydroton is the media of choice but it is way too expensive for my 16 square feet of grow bed.

I am leaning towards using lava rock on the bottom and hydroton for the top layer.

Here is a link to the lava rock http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?s...
the propaganda says 1 bag will cover 6 S.F. so I am planning on buying 4 bags of the stuff for the bottom layer ... does that sound right?

Also I think 1 bag of hydroton on top might be enough? What do you folks think?

How much SF area would 1 - 50 liters bag of hydroton cover?

Thanks for any advice or recommendations, 
Bob

[Bob Vento]

I am reading reviews from some who have said that the red washes off of these lava rocks! That can't be good for the plants or the fish. Why can't I just find ordinary lava rocks that won't harm my system?

[Jonathan Hall]

3/4 gravel seems to be a great choice for affordability and it works great.

Make sure you bring a glass of vinegar when you go gravel shopping. Look for a quarry to get it on the cheap. Take a few samples of the stone candidates and put them in your vinegar. Watch for bubbles. If you see them, try something else. You want to find an inert rock. No limestone! River gravel typically is a safe bet but is pretty smooth. If you can find something more porous that may be a better bet but I wouldn't sweat it too heavily. Really depends on the type of system you are building for any slight edge you may get. The river rock has the benefit of also being very easy on your hands for digging around in. Lava rock = not as fun.

Maybe call some building / contractors and ask where they go for theirs gravel. It should not cost much at all.

[Jon Parr]

3/4" drain rock, no fizz, from a rockery not a lumber yard. Around here, the cheapest round river rock sold as "drain rock" is already washed and screened for size, and delivered to your driveway. 

The red that washes off lava rock is just lava rock dust, and is not harmful to fish or plants. Don't sweat it. The cloudy water will settle in a few days and lava is a great medium, though again I'd opt for the larger 3/4" size if you can find it. 

[Jon Parr]

50 liters is 1 3/4 cubic ft, so if your 16 sq ft of GB is 1 ft deep, then you have 16 cu ft, requiring 9) 50 L bags go straight hydroton. If you want it for a 6" top coat, then half as much, or 4 1/2 bags. If you want it 4" deep, then 3 bags. Etc.

[George]

Being in Miami, you have access to 3/4 inch Stalite at Conrad Yelvington, if you want to use it.  There is much discussion about it on this site already.