Backyard Aquaponics
A place to discuss aquaponics

Don't think so Decalsby (could be wrong ) problem is even with size shape also matters, and all rock dosn't weigh the same.

JT, been thinking of weighing my Scoria, just so I knew, and publishing the results.
I could never find the data anywhere.
I think a thread might be started on this, but I'm not starting it without data :-)

along with the weight, could be the displacement, or better, the inverse displacement (how much water can fit about the media)

Think Aquamad? did a water displacement exercise, but its going to be slightly different for different media ie pea gravel v blue metal (and that being inconsistent in shape would be a bugger
Think we just go with the 'about' measurement.

OK sleepe, I'm considering building a bed, when it's full it will be about 40% water... how heavy will it be? I need my stands not to collapse.
If you build in fudge factors, then so do the designers who tell you what grade steel to buy, It was recommended to me that I use 75x50mm with wall thickness of 6mm steel!! WTF? that would hold much more, (I think)
it's the weight more than the volume of water I think would be handy.
How much room does 10mm scoria take up versus the 20mm I have? how heavy is it?

This is why 'about' has been insufficient for my design needs.

Thought you over engineered everything KP

Scoria is in a different class, think you will need scoria wet weight. Then apply the 40%, and the just in case factor

Sure do Sleepe,
Check out my thread for my 100 x 50 with 6mm wall thickness... couldn't lift it.
And I only overengineer when I can afford it.
The steel was free so... I could afford it, I just couldn't lift it :-)

50x25 with 2mm wall should be enough for a 2m span holding scoria. This is a recommendation from a robot stand designer.
It it looks like bending, 6 legs would fix it cheapest, with only 1m spans then. Adding the legs later would bend it back level he says (he can be a bit rough, but he knows it's agricultural <- technical term)

Hay, sorry I haven't been around much lately. Kinda busy with other things.

I have plastic over most of my system so got a bit of protection from the cold, I don't think my water ever got down much below 60 F at the coldest. No fish losses due to cold though they were not eating for a while. Now my water temp is back up to 70 F and higher and the fish are eating again. I'm thinking I won't bother getting tilapia again in the future once we eat the ones we got since I would rather not have to keep the whole system all covered up to keep the water temps up. It still gets rather hot under plastic on most days and that just doesn't work as well for many of my favorite crops.

The lights. Well I'm not the best to answer about MH or HPS lights as I have only used Florescent grow lighting for salad crops in my indoor hydroponics over summer when it is too hot out to grow salad outside here.

As to media and price. I've gotten the 1/4"-1/2" brown river rock for $50.10 a ton but luckily I don't live too far from Pebble Junction here so I think they only charged me $90 for delivery of 6 tons of rock.

The brown river rock they told me takes about 1.25 tons to make a cubic yard.

I think you'd have to know the actuall density of the rock, gravel, or clay ..... for instance, Granite is much more dense than Marble, hence, Granite is much heavier than Marble etc., etc., ....... (I used to make countertops )

Typically, 3/8" pea gravel will weigh the same as 1.5" similar gravel as it contains the same amt of air space. Most rock is pretty similar, with exceptions: some lava will be quite a bit lighter (foamed rock) and some types of rock are far heavier than others, but for most rock you can figure 1 ton to 1.5 tons per yard. No charts I know of, unless you want to pick up a copy of "the pocket ref"*, an amazing book of data and information: everything from density of planets to conversion from chains to meters to specific gravity of materials to airport codes. But you would be better off just giving someone a call and asking the weight or assuming TCLynx's 2500lb/cubic yard (90lb/CF).


*(http://www.google.com/products/catalog? ... ps-sellers)

My numbers were for the mostly quartz type river gravel. Granite will be heavier, limestone will be lighter. Granite will cost more, limestone might be cheaper but you probably don't want limestone pea gravel for an AP system, or at least not much of it.

If you can get a really really good deal on lava rock, that is pretty good in an ap system except that it is difficult to dig in and really needs to be washed well (even after a good washing, the water is gonna cloud up for a while with lava rock but there are nutrients in lava rock that are not in river rock.)

What TCL says here is good advice . In addition to my earlier comment on weights, etc., I want to make this additional comment ..... In fabricating granite and marble countertops, I learned the following: even granites have different densities and therefore different weights; Absolute Black granite will weigh more that Australian Waterfall granite (Black with grey streaks or waterfalls), as you move into the various colors, brown, blue, green, grey etc. it becomes less and less dense/more fragile and therefore lighter in weight (even though it doesn't feel too light when a slab falls on your leg and damages your ankle and knee - personal experience ). The same thing goes for marble countertops, white is the lightest/most fragile, while the darker ones are actually more dense ..... (my personal advice, avoid the pretty brown one with swirls of red/yellow/pink/ or white amongst the chocolate brown for your countertop). In other words, pay attention to what you're buying and ask the gravel company about the weights, don't try to get exact numbers from anyone else other than your supplier, as TCL has mentioned above, all rock is not equal, either in use or in weight ...... just my two centavos

seems like rock is way expensive here from the sorces i have found.

$130.00 per yard for .50 to.750 (1/2-3/4) sized in bulk (i haul). or 3.50 per 50 pound bag from lowlifes i mean lowes or walmart

i really want to use the larger medium but may have to mix with that tiny filler i found for 50 bucks per ton.

im worried the small medium will clog my drains so at very least ill add screen and possibly even a full tube in the bottom (prolly drilled pvc covered with screen)

and have the bottom 1/3 (at least) filled with larger stone as i can afford it.

i did find some poly growbeds in 2x1x6' for 79.00 each at local farm supply store. im still struggling to find a pump
i like, can afford, and will do the job.

I got my rock from Pebble Junction over in Sanford. They have the 1/2 inch brown river rock for about $52 a ton. I don't know if you are close enough to make them a possibility though. I was able to get delivery of 6 ton and I think the delivery charge was about $95. Still a pretty big cost but if you are close enough, it may be the cheapest way to get appropriate gravel.