Backyard Aquaponics
A place to discuss aquaponics

I'm hoping someone can help me with some numbers, I need to get or make staging for the centre isle of my hope-for polytunnel, but I'm not sure how much weight it needs to hold. My expected grow beds will likely be 130l dog bath type, is anyone able to give me a rough figure for how much that might weigh when full of cheap heavy gravel in a constant flood setup? I'm pretty sure the measurements were 4' × 2' × 1' if that helps. Thanks for any help!

Water = 1 Kg / Litre
Gravel = (about) 1800 Kg/Litre

Do the math.

Damn that's some heavy gravel! Wouldn't wanna be washing that...

Yea, way heavier than my washed 14-20mm river gravel, which is 1300kg/m^3

I was thinking that sounded very heavy!

I an using 90mm/by 35mm treated pine, 2400/970/600mm high, but I am using 500ltr of the clay media which is around 150kg, plus around 120ltr of water at 120kg, if you went for steel I would suggest 76mm/38mm,1.2mm thick box tubing, or patio tubing,
I am not sure if this helps, but you could always screw two pieces off 90mm/35mm together giving you better centre strength, offcourse you could share the load with two cross beams as I have done, at 800mm apart approximately, but in your case maybe less distance,
If I knew how to show a video that didn’t max out everyone’s wifi I would put it up,

I hope this will give you some idea as to what you can do,

Here in Queensland, we live on the largest Blue Rock or Basalt, deposit in the state. Solid Basalt has a mass of around 3000Kg/cu. m., Broken Basalt around 2000Kg and the crushed Basalt (about 15 to 20mm pieces) is 1850Kg/cu. m. The latter is what we have to 3/4 fill our grow beds with a topping layer of Canna Clay Balls. I'm sorry I mistakenly put the mass /LITRE not /Cubic metre posting.php?mode=quote&f=8&p=468449#
Anyway, I wash it in my cement mixer with a steady supply of water and have never had any trouble doing it this way.

Cheers IanK