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Bubba5

Depth of grow bed????

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Back again. I will be cutting my IBC tank this weekend and would like to know a good depth for grow bed. Because have seen a few how to's on u tube and most say 30cm but i seen one bloke reckons 40cm is better. And what size pump is good for this tank? PS would i be better off putting tank in shade and grow beds in sun? I do have a place i can do this but i thought tank in sun would be good for water temp? Cheers thanks everyone

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Your question will stir up much debate here. Many folks in the hobby say 300mm, but others feel it's more than you need. Here are my thoughts if you don't mind me sharing.

Depending on your TOTAL system - GB volume, external filtration, etc. deeper GB's can give you a little extra surface area for bacteria to develop. In many systems, vertical space is easier to come by than horizontal space. Deeper beds don't hurt anything. That said, mine are about 230mm deep and I grow big stuff and small stuff with no issues. The key is that I use heavy river rock for media to support the plants. A shallow GB with only hydroton will barely support a dandelion.

Plants will grow fine in 200mm, or 300mm or 400mm. You need to balance your bio filtration needs and your budget - for instance, what depth GB's can you get a killer deal on? Then think about how much expensive media it will take to fill them up. Just got to balance your priorities.

Hope that helps.

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Hi Bubba,

When it comes to grow beds, surface area is much more important, in terms of bacterial colonisation, than depth.

Currently, I'm aware of grow beds that range from 120mm through to 1 metre deep.

As Tpilk says, it's about having sufficient bio-filtration to deal with the wastes generated by your fish.

If you include mechanical and supplementary bio-filtration into your system designs, the number, size and depth of grow beds become irrelevant.......and your range of growing system options broadens considerably.

Gary

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Hi Bubba5

I have made some IBC grow beds cutting them in such a way that I get the maximum grow bed surface area from the tank. This is done by cutting the IBC vertical instead of horizontal. When cut this way the pieces won't fit into the cage. That is fine for me as I like to support the grow beds in a treated pine box. 300mm depth is a good size it takes 2 x 150mm boards to cover the sides.

Remember that your grow beds are in effect a bio filter. The deeper you make the bigger the bio filtration capacity.

Cheers

Joey

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OK, to stir the pot even more. Make your grow beds deep enough to support the plant you intend to grow. This is the only real requirement. You just need to make sure you have enough volume to support the amount of fish you need to grow. 30 cm has been used with success, i have used growbeds as shallow as 10 cm. A member on another forum was growing corn in an full IBC as a growbed. A deeper bed is better for supporting tall plants such as tomatoes or peppers. A shallower bed may be more economical for lettuce and herbs. A shallow root plant will grow in a deeper growbed, but a deeprooted plant will not grow well in a shallow one. Tpilk has a very good point about media type.

This is my main guidline questions for growbed.

What is available that will support what I want to grow?

What is affordable?

What is easy to plumb?

What will last?

As far as the ibc, you will have better luck with it in the shade and the growbeds in the sun.

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Hi,

A shallow root plant will grow in a deeper growbed, but a deeprooted plant will not grow well in a shallow one.

As this post evidences, you can grow almost anything in a shallow bed......including pawpaw (papaya) trees......all 10, or so, of them.

I agree with the notion that the media type is a much more important factor than grow bed depth. You can support corn plants in a 100mm bed filled with gravel while the same corn plants will topple in a stiff breeze in clay pebbles in a 300mm bed.

Ultimately, it comes down to what you can afford......and what you can get.

Gary

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Cheers thanks everyone i think ill be going for 300mm and i found someone close by selling clay pebbles i think ill need about 6 bags [45L per bag] he said he will do it for $195 hope thats not a bad price

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Hi Bubba5

I used river pebbles topped with hydroton on me first grow bed. Since then I have used just river pebbles or drainage scoria. From now on the only place I would use hydropon is in the net pots of DWC growbeds. I think in aquaponics hydropon is simply a waste of money. Plenty of good alternatives. (River Pebbles, Drainage Scoria and Blue metal gravel)

Cheers

Joey

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Very good information here provided regarding the depth of the grow bad. keep sharing such a nice information it is really helping us in growing the plants.

Hi Moderators......Jacobtaylar and David Harritz have some things in common. First is their use of the same avatar.....and second is their inane style of posting which serve as an excuse to insert a gratuitous link to something that they are selling (see below).

In Jacobtaylar's case it's.....Find the led grow lights easily.

Feel free to get rid of such posts......and to ban them.

Regards......Gary

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I've grown in GB depths from 4-24 inches (~100mm-610mm). My best beds have usually been 8 inches (~200mm) deep.... and get this, continuous flow (a flow/drain method many consider antiquated) at a water depth of 4 inches . Your mileage may vary. :)

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I've grown in GB depths from 4-24 inches (~100mm-610mm). My best beds have usually been 8 inches (~200mm) deep.... and get this, continuous flow (a flow/drain method many consider antiquated) at a water depth of 4 inches . Your mileage may vary. :)

On your growbed with continuous flow, do you use have one point of entry for the water or several spaced throughout the bed?

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At first I use 300 mm deep gravel beds ( water level 250 mm) with F/D with autosyphon because everybody say that's a basic set up of AP, and it works ok to the point that I need to wash (clean) it. :frown:

Now, I'm on 150 mm deep GB, half is continuous flow (water level 70 mm), half F/D (water level 120 mm), to see what works for me the best.

For now it's tie.

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On your growbed with continuous flow, do you use have one point of entry for the water or several spaced throughout the bed?

Hi Ravnis,

Most of them use a submerged pipe running the length of the bed with small slits cut in the pipe, and there are drains on both ends of most of them. I originally had set them up to be bog filters filled with aquatic marginals, and then changed plans and thought I'd try them as traditional GB's and they've worked great.

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I have come to the following conclusions in regards to grow bed depth. If you are using a flood and drain system, I feel 12 inches is correct for most plants. I set my water to drain when it gets within about an inch of the surface. My drain is set where I always have at least an inch of water in the bottom of the grow bed.

It's my belief that different zones are created by the bacteria in the grow media. In the bottom where there is always water, you have a high concentration of bacteria breaking down waste. As the waste water filters down through the grow media it will settle out at different levels and establish little pockets. So basically you have 10 inches of varied levels of bacteria breaking down the waste and feeding the plants.

By leaving an inch or so of water in the bottom of the grow bed, you also establish a little bit of a buffer in the event your pump quits working. The plants will at least have a little water to hold them until someone notices and fixes the problem.

If you are running a continues flow system, then you are not concerned about establishing bacteria in your media. You should be running a bio filter of some kind which houses the bacteria and breaks down the waste prior to arriving at the plants. Therefore, you only need what ever media it takes to support your plant. Or no media at all as with a raft style system.

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Hi,

I have come to the following conclusions in regards to grow bed depth. If you are using a flood and drain system, I feel 12 inches is correct for most plants.

In truth, it doesn't matter....regardless of whether you're using flood and drain or continuous flow. When it comes down to bacteria, grow bed area is more important than depth.

It's my belief that different zones are created by the bacteria in the grow media. In the bottom where there is always water, you have a high concentration of bacteria breaking down waste. As the waste water filters down through the grow media it will settle out at different levels and establish little pockets. So basically you have 10 inches of varied levels of bacteria breaking down the waste and feeding the plants.

That probably sounds logical but the bacteria will thrive anywhere that is moist and well-oxygenated. Having too much in the way of solids in a grow bed is to be avoided because (as with any biological filter) the lower the solids loading, the better they work.

If you are running a continues flow system, then you are not concerned about establishing bacteria in your media. You should be running a bio filter of some kind which houses the bacteria and breaks down the waste prior to arriving at the plants.

If you run mechanical and biological filtration (and you should) then nothing else matters. You can use any type of growing system (or none at all). The bacteria will grow in a continuous flow grow bed in the same way that they do in a flood and drain bed.

Gary

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I run a 6 inch growbed.. works just fine. You really only need 12 inches or more if you don't have filtration..

I agree. If you are running a bio filter then you are not concerned with establishing bacteria in the grow bed itself, the bacteria are working in the filter system. Therefor all the media is for is to support the plants.

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Hi Littlewolf and Pugo,

Some of the longest running grow beds in Australia (continuous operation for over 7 years) are less than 6" deep and are part of a system which has no filtration outside of the grow bed itself. The systems (there are several of them) are powered by goldfish.

Gary

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I agree, solids in the grow bed is not a good thing. When I mentioned bacteria existing in zones, what I was talking about was the build up of bacteria in the media as it matures. Depending on the media you are using, some media has better pockets for bacteria to colonize then others. I like a 3/4 inch media, it seems to me to have good pockets for bacteria to grow in, lots of available oxygen. I see lots of people using a small pea gravel or something similar, and it seems to me this smaller stone just doesn't allow good surface area for the bacteria, nor does it allow for good oxygen flow.

As the grow bed matures, I would think it would be natural for the bacteria to grow better further down in the media. As the water comes in from the top, and drains out the bottom, the bacteria is getting washed down into the lower pockets. Therefore, if you have a little depth to your media, it just stands to reason you would have more bacteria build up, which is a good thing.

As for filters. On my flood and drain system I do not run a bio filter or mechanical filter before the grow beds. I do have a 55 gallon settling tank with a skimmer on top. The water is pumped from the fish tank up into the barrel, the solids settle to the bottom, a skimmer catches any floaters or solids that try to drain over into my grow beds. So far the system has worked well. My barrel has a drain valve in the bottom, so occassionally I drain off some of the solids. I try to keep a small level of solids in the barrel however, because I'm sure I have bacteria growth in there as well, which is good.

I'm considering raising Crayfish in the bottom of my fish tank along with the Tilapia. From what I have read, the crawfish help keep the solids in the sytem down to a minimum size.

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Hi Littlewolf and Pugo,

Some of the longest running grow beds in Australia (continuous operation for over 7 years) are less than 6" deep and are part of a system which has no filtration outside of the grow bed itself. The systems (there are several of them) are powered by goldfish.

Gary

I'm guessing they have lots of surface area? If you have 6" deep media, and big wide beds, I can see that working just fine. Because of their shallow media, are they limited on what type of plants they can grow? If you are growing green leafy vegetables, I wouldn't see a problem, but would tomatoes, peppers, squash, vegetables like this do well in only 6" of media with no bio filter?

I am currently building a completely new system, and I am planning on having a variety of grow beds. I'll have 12" media in a flood and drain system for my larger plants like tomatoes, peppers, squash, etc. and shallow beds for faster growing leafy vegetables like lettuce, kale, etc. I'm also thinking of having some continues flow beds with floating mats in them. The continues flow beds will be between my flood and drain systems and the fish tank.

My new green house currently under construction will by 18'x28' when finished, with the entire thing dedicated to aquaponics. I'm planning to test out several theories of my own.

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Hi Littlewolf,

I'm guessing they have lots of surface area? If you have 6" deep media, and big wide beds, I can see that working just fine. Because of their shallow media, are they limited on what type of plants they can grow?

Based on what I've observed, there is no limitation on the type of plants. The only caveat is the type of media in use. Clay pebbles tend to not have the same anchoring capacity as 20mm (3/4") gravel. Plants like corn do much better in gravel than in clay pebbles.....and corn is just as good in 6" as it is in 12" of gravel.

If you are growing green leafy vegetables, I wouldn't see a problem, but would tomatoes, peppers, squash, vegetables like this do well in only 6" of media with no bio filter?

Once you resolve the question of plant support, let's remember that tomatoes and other vine crops grow in NFT with no media at all.

I am currently building a completely new system, and I am planning on having a variety of grow beds. I'll have 12" media in a flood and drain system for my larger plants like tomatoes, peppers, squash, etc. and shallow beds for faster growing leafy vegetables like lettuce, kale, etc.

There's no doubt that that will work. If your reason for opting for 12" deep beds is to avoid using supplementary filtration, you should understand that you lack the productive capacity and resilience of the same system with filtration.

I'm also thinking of having some continues flow beds with floating mats in them. The continues flow beds will be between my flood and drain systems and the fish tank.

If I understand you correctly, (and by "continuous flow beds with floating mats in them" you mean a raft tank) hat you've described is termed a "hybrid" system. Once again, it will work - but it will be more productive and resilient if you incorporate simple filtration arrangements into the design.

My new green house currently under construction will by 18'x28' when finished, with the entire thing dedicated to aquaponics. I'm planning to test out several theories of my own.

Looking forward to hearing how it goes for you.

Gary

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