Backyard Aquaponics
A place to discuss aquaponics

Hi all'
I have bought a nifty little greenhouse from Bunnings and want to start up a small system in there. It will house all the 'canary' fish ( goldfish) I use in my big system when i want to replace them with the real thing after it has stablised - fish i can eat.
Anyway this greenhouse has shelves but they are WAY too fragile to support the weight of my 50 L recycle tubs I use as grow beds.
I'm going to have big biofliter tubs full of scoria sitting over the tanks to filter the water and want to use the most lightweight medium i can for grow beds above the tanks and biofilters on the shleves.
Questions: Am right in asssuming that perlite is much lighter than scoria gravel?
Is there something even lighter I can use as a grow medium considering that most of the filtration will occur elswhere?
If perlite's the go - where do i buy it? Is it available at the 'Temple of Hardware' ( Bunnings) ??

Thanks for all your thoughts.
Aeon

are the shelves a permanent feature of the green house? If not maybe some of those metal kit shelves might work for you (if you can't sort out some lightweight medium)

Perlite is indeed very light. Vermiculaite is another one that is used and is lighter than perlite. I would imagine a 50:50 mix would be the way to go as this is what is commonly used in hydroponics. Bunnings does sell it in small quanties, you may be better off finding somewhere that sells it in big bags it would work out cheaper.

Hi Jaymie,
yes the shelves are part of the whole structure but I know the metal ones your talking about and I have considered reinforcing the greenhouse with them as they would fit in there. The main problem is the legs of the sehlves would then be in the way of the fish tanks. I love the challenges of design but this is driving me nuts! I really wanted to use up some of the assorted containers and materials that are accumluting around the yard and driving hubbie mad, and trying not to buy more new stuff for this system. Hence leaving the greenhouse the way it is and just buying some perlite. But Ive got so much spare gravel!!! Its just too heavy to use on the shelves.
But maybe you're right. if I reinforce the shelves somehow then i can use all that bloody scoria gravel in small grow beds. And I DO have about 4 of those metal shelf kits lying around....

Well projects give you something to do while you're brooding! For my first I built a concrete block wall and a shed! The second one was while we built the cubby house! Climbing ladders at 8 months is fun (watch the husband squeal!)

Hooray ! I'm not the only one! - i cant wait to show my husband your email.
I think we are a special breed though - most of my girlfriends think I'm insane and ask me why i dont keep a scrapbook or do indoor craft projects instead...

yawn! the only thing to worry about is fitting in the work space

I think the last time I priced Perlite it was about $28.00 per 100 litre bag and you should be able to get it from most hydroponic shops.

Tim's right.....a 50/50 mix of perlite and vermiculite is a common hydroponic media. The only question is whether you are going to use continuous flow or intermittent nutrient feeds. If you're going to go with continuous flow, I'd leave the vermiculite out (the mix may get too wet) but if you're going to use timed, intermittent feeds, the mix may be the go.

If you experience problems with the perlite or vermiculite blowing around, you can use a layer of light expanded clay aggregate (like Hydroton) to keep the perlite/vermiculite in place.

If you want a lightweight media for your bio-filters, you might want to think about polystyrene beads (like you use in bean bags).

Here's an aquaponics site that uses perlite http://www.aquaranch.com/

A while ago I found somone using PVC ribbon as a biofilter media. He puts 1/2" pvc pipe on a metal lathe and just goes crazy. He had one blue barrel-full filtering his 8,000L koi pond. It is due to the incredibly large surface area.

I have a friend who uses 4mm poly dripper tube cut into 1 cm lengths as a lite medium in a blue barrel biofilter, it works really well apparently.

p.s, my wife was mowing lawns full time with me until she was 35 weeks pregnant with our first! 2 weeks later she was admitted to hospital and induced with high blood pressure LOL

Wow - some VERY creative ideas there!
Gary - if I can use polysteyrene in the biofilters I am assuminng that bacteria can grow on it, right?
If so - could I not use polysteyrene beads in grow beds as well and just cover them with a thin layer of gravel to stop them from blowing away? Also, I wonder as the beads are so white would I need to cover them in the filters to make it a bit darker for the bacteria to grow?
Thanks for all your great ideas everyone
Aeon

apparently the bacteria are okay once they affix themselves to a medium, they don't like the sun when they are free floating
About the idea of using polystyrene beads in the grow beds - I think a big decider would be what you want to grow - a number of people have even found that Hydroton is not heavy enough to keep their plants upright... so look into that first as if your plant will grow tall (ish) it could land up toppling over