Backyard Aquaponics
A place to discuss aquaponics

Ok, cut down the weeds and propped up (temp only) the proposed beds to give everyone an idea of where I'm going and invite some feedback.

Books on the way, unfortunately didn't make it here for the weekend...
guess that means I'll have time to think about growbed support structure

Anyway you can probably get the rough idea from the pictures...

What they don't show though is that I'd like to help shade the growbeds and utilise the space above them by a lush covering of strawberries utilising an nft system, converted of course to AP, but capable of standalone nutrient feed if required.

6 x 2mtr oval nft but utilising the nutrient drip fed to pots (with hydroton) above the nft holes, thus using gully just for collection/circulation back to tank.

This way I can get about 4 plants/pot and approx 35 pots ==> 140 plants, will need some shade cloth/netting over everything.

Hydro system originally came with its own tank (so can be standalone) which I can always use to supplement if needed or just adapt and autosiphon to growbeds below.

You'll notice I've got a spare barrel under the stairs....

Question, tanks 700ltr (1.2m x 645)... I have about 200ltr water capacity in barrel beds plus maybe another 50ltrs in the nft gully system so all up that's 250ltr in the system...

Only leaves 300 approx in the tank i.e I'm circulating nearly 50% of system. Does this leave sufficient capcity for the fish in the tank?

I know it obviously depends on the timing of the various growbed siphons, but should I maybe utilise the spare drum (cut down?) under the stairs and siphon drain everything at once back to tank or uses as a backup gravity fed siphon if the main tank gets too low (maybe use as a fingerling tank) and just siphon growbeds directly back to the tank.

Hope it all makes sense... comments

OK ... pics of the nft setup... to become AP i might add

Hi there to the anonymous "guest" who checks out my thread everynight.

PM me or post a hello, I'm curious.

If you're nearby and doing or thinking of doing something similar then get in touch

Hey Rupert,

The system looks like it's coming along nicely.

The question about water in the system and whether there is enough when everyrhing is pumping.. When your growbeds are filled with gravel there is only about 10-20% air space, so if your using 4 half barrels that should be 10-20% of 400L. Thats only 40-80L needed to fill your growbeds with water when they have gravel in them, not too much water..

Thanks EB, misunderstood some of the posts thought it was closer to 50%

Hi Rupert,
I don't think you misunderstood the posts, I've seen people quote 50%, too. I think you need to measure against your own media. Some folks have media with more air/water space, some have less. My Delaware Valley River Gravel comes out to about 30%. The prescribed methodology is to measure out a known volume of media into a bucket, then fill to the top of the media with water. You can calculate a % from that.

There have been a couple of tests done and it depended on the medium used, some came out around 40/45% water and so to add a safety factor, 50% has been used (also saves me taking off my shoes to calculate )

The 50%ers must be pretty course medium.....

Thats a lot of airspace between particles... You should definately go and find a suitable medium and give it a test.

i think 50% was for they hydrotron, wasn't it?

Could have been - I think AA was doing some experimenting on it

Thanks to all, I'll try your bucket method Steve

Some further help on water volume needed...

http://www.backyardaquaponics.com/forum ... .php?t=770

Thanks Asitis, that's the post I was thinking of, thouight it was Steves

Okay, got some gravel for the grow bed and remembered about the percentage of air in the medium discussion so did a test:

One by 10 litre bucket (graduations on side)
10mm (1/2") drainage gravel pre-washed

Filled bucket to mark with gravel
added 4.2litres of water to reach the 10 litre mark, which is in the range of 40-45%

A figure of 50% has been used as a safety measure to take into consideration of evaporation/respiration of water.

As plant roots grow this area will diminish but by using 50% as a guide, then the size of a sump/fish tank can be established, remembering that sufficient height is needed for the pump and any fish to swim in on “the worst case” scenario.

Hope this is of some help

That about nails it.

Thanks EKB