Backyard Aquaponics
A place to discuss aquaponics

Just wondering how deep the average grow bed is?

I've not had alot of experience growing plants in hydo-conditions
What would you (everyone) consider to be minimum and maximum depths for a growbed. Or at least how deep are yours?

My main reaosn for asking is i often have access to old kitchen equipment from commercial kitchens and pubs which may be usefull as growbeds, tanks and other great bits and pieces, and i'd like to know whats good for what.

thanks

Ek, 30 cms is recognised as the optimal depth to support the required bacteria. mine are 40 cm's will fill them to 10 cms from the top

thanks Monya, it's good to know but a shame, because i often get 150mm deep perspex trays that i was hoping to use.

guess it'll be fighting fish instead

EK

Incorporate the perspex trays into it somehow if you can get them for free. You just need a decent amount of gravel beds for the bacteria to grow, IMHO nothing stopping you using the perspex trays like you would guttering or poly pipes.

IMHO this sort of depth is sure to present problems with clogging. Because of the amount of water changeover sought in aqua systems, I think that problems of damming are a greater issue for us than they would be in a hydro setup.

That is true VB, I am finding that my strawberry tower has problems now with cloging, Root balls etc. I believe the grow beds just would not work over time if less than 300mm deep.
Muzza

Fair enough, happy to be vetoed!

Hi,

I have two questions:

- Why does a grow bed have to be 300mm deep?
I can understand the root problem if the plants are the type that develop big roots but why couldn't a bed be 150mm deep if it was going to be used for lettuce and soft herbs for example.

- Why can't perlite be used as a grow bed medium? It's a fraction of the weight of even clay aggregate balls and much cheaper, too.

I don't mean to be confronting but sometimes things become accepted simply because people say them often enough. I accept that there may be good reasons but I haven't heard them yet.

Can someone enlighten me?

On perlite. I'm not sure regards this as the chemical analysis varies according to source, the source figures are readily enough given though. I have no idea what aluminium oxide etc means to fish when it comes in expanded rock form. Ours even has titanium hehe, tough fish.

Pumice would be great but it floats too much with beds settling. We have a huge lake the shores are pumice so can't be bad for fish.

Growbeds, yes why can't leafy veg have less, maybe the temps swing too much? I'm a growbed noob.

Garyy,

Once again i was going to put this info in another section, but you raise a good question.

We heard much on the week-end of how gravel system are APPARENTLY inferior, clog, and are too much trouble.........

My suspicion here is that the gravel bed parameters are the KEY to a sucessful gravel system. I believe that Joel has modeled his systems around the speriano's who have been running gravel systems for 15 odd years and rarely (if ever?) clean them.

After hearing all the negativity on gravel growbeds, i have the sneaking suspicion that joels volume: depth: diameter are a "sweet spot" for this style of aquaponics.

One of the major problems that people had with gravel was that they clogged. Maybe its a factor of the flood and drain, maybe it a factor of the depth and gravel size. I think most other attems were on a continuous flow system

Anyway what i'm sayng is feel free to modify and play arund with depths and stuff like that, just realise that pretty much everyone else has "canned" the gravel beds because it didn't work for them. It was quite funny hearing all that, becasue we've all seen joels picutres. LOL

What are they using then. DWC?

They call it deep water flow. yes it is DWC exactly.

It amazing to see the surperfulous hardware required, a 2x1 meter swirl clarifier, a filter screen assembly that requires cleaning of the filters twice daily and 4x 4m high biofilters. I'll post some pictures of the poly house section when my GF gets back, she's stolen the camera for the day. Once again, we know better than nature...

My guess is that there is a bit of old fashoned academic snobbery going on there Steve, EB has worked it out "Hands On"
It is clear within EB's book and by the pix's that 300mm deep has proven to work.
My grow beds will all be 300mm deep no question.
I have found that the strawberry tower is clogged badly now. It is made from 90mm pvc, so I will make one up soon out of 200mm pvc or metal pipe (just have to find some) So I guess the clogging is an issue in some systems. Perhaps the grow towers need to be 300mm dia to work properly. ??!! When I find out I will post the results.
Muzza

I was wondering about the straberries MUz

I think it is a function of depth to width.

I still pan on having a few DWC nodes, but it is my opinion that the initial system should be built as close as the book "spec" and then all other nodes plumbed in to the discharge of the beds and then return to the tank.

This serves multiple purposes.

1) a flood drain cycle on the gravel grow bed is also a flood drain cycle on any other down line node. For example: beds flood, then beds drain to a DWC channel, which then drans back to the tank

2) The bed functions as the primary sediment filter and bio filter media for the complete systems, should not be much clogging down line

3) nup, thats it

Yep, Joels got it sussed with beds, follow him to the letter while taking your own environmental factors into account and you'll have a big grin on your face.

And I've some great Aqua DWC tricks and experience. Some of which will be in construction in my system very soon.

That's a great idea Steve, the beds to channel, remember the DWC wants a lot of flow in comparison to the beds, so figure the ratio of beds to channel and it should work great with lighter feeders giving the water a 'final polish'.

I've a feeling it will slow DWC buckets down a bit taking the largest nute sources to the plants in the beds first as buckets have the big feeders growing in them.