Backyard Aquaponics
A place to discuss aquaponics

I have been trying to track down a source of bulk lava rock here in the states close to me and finally found some that I can buy by the ton. The issue is it is 1 1/4" size or around 30mm. Is this to large for using as a grow medium or will I be fine with this? The bags available at the hardware store are $3.80 for 0.5 Cubic feet and I need to fill 4 IBC growbeds and trying to find a cheaper route.

Thanks
Mallow

That sounds kind of large to me. I have lava "pebbles" (bags from one of the big home improvement centers) in my IBC bed and I'm not real fond of them - kind of rough, hard to move around, and hard on the fingers. I much prefer the pea gravel in my other bed. You could probably use the bulk lava rock in the lower part of the GB and top with 3-4" of the lava pebbles. It would likely get mixed up eventually but it'd probably work ok.

That's what I did. Lava rock on the bottom, small river rock on top. It only gets mixed up when I pull out a big root, but not too bad.

After looking everywhere for smaller with no luck and most other options seem to mess with PH I guess I will save a while longer to be able to afford expanded clay balls. Thanks for the input.

Landscaping uses the big stuff... to get smaller, it costs more.

However, I have been wondering about a 'barrier' between the small and large material. It wouldn't be perfect... but there is 'graph-like' plastic that insets lighting boxes... you can get 'plastic sheet' in a variety of styles, or you can get this stuff in a variety of sized- squares. It cuts fair easy with tin snips, and I originally got it to help my students 'make paper' as a project to connect them to their writing... the open squares are roughly 1/2".

Any thoughts?

It's unlikely that plastic is food-grade, FWIW. Unless you're really giving your beds a beating, I doubt it's necessary.

Mallow, I tested the river rock at the store with vinegar before I bought it. No bubbles, and my pH has stayed low.

Thanks Jake.

Mallow, this is the lava pebbles product I used: http://www.menards.com/main/building-materials/landscaping-materials/ground-cover-materials/red-lava-pebbles/p-1934703-c-5784.htm Don't know if you have a Menards around there or not, but someone should have a similar product. It's smaller than the normal lava rock you see in landscaping beds.

Can you not find pea gravel (small river rock)? I bought this from Home Depot: http://www.homedepot.com/p/t/100318444?storeId=10051&langId=-1&catalogId=10053&productId=100318444&R=100318444#specifications I'm sure I could have gotten it cheaper at one of the local gravel suppliers, but HD was more convenient when I needed it.

i use 14mm (just over 1/2") and find it perfect

i use 20mm 3/4inch and it works sweet

I use media thats all about 10-15mm or roughly 1/2 inch.. The expanded clay that pretty much everyone uses is 8-16mm in size...