How deep should a grow bed be?

[HealerOliver]

I have found a source for my grow beds. This fiberglass company will make them just about any size I want. So, my question is; for an 1 square meter grow bed, how deep should it be?

Oliver

[GaryD]

Hi,

Grow beds can be any depth from 150mm to 300mm (6" to 12"). They can be even deeper but they'll cost more to make and they won't work any better.

The argument in favour of 150mm grow beds over say 300mm ones is that they require less media which, depending on your choice of media, means half as much work to fill them and/or half the cost to buy the media.

Conversely, you can have twice much growing surface for the same amount of media/expense.

My grow beds are 300mm and 350mm deep respectively.....because that was what was available.

Gary

[Murray]

Another view in favour of 300mm (1 foot) deep grow beds is that it works much better with deep rooted veggies such as tomatoes and corn. The shallower grow beds are fine for such things as lettuce etc.
Also, by employing deeper grow beds there is just more volume of everything which tends to add more stability to any system.

[Dufflight]

How big is your fish tank. In my larger system I use very deep GB's to increase the amount of media for the bacteria. On smaller FT's you may not need this. Think mine range from 40 to 70cm.

[Outbackozzie]

I have beds up to 1m deep, which increase the temp stability greatly.

I'd say 300mm is the minimum for corn and tomatoes etc. Even then they fall out of hydroton

[GaryD]

Hi,

If you'd like to see a wide range of vegetables and herbs (including tomatoes and corn) growing in 150mm deep beds......click here.

Gary

[Outbackozzie]

Yes, I grew them all in under 75mm of media as well - but it is undeniably better to have more depth.

[GaryD]

Hi OBO,

.....but it is undeniably better to have more depth.

I sense that's the feeling some quarters but are the reasons so compelling that you'd want to pay much for deeper ones if you were starting from scratch.

If you have sufficient nitrification to cater for the size tank that you have and you are able to effectively control the environmental conditions to which your system subject then I contend that it doesn't much matter.

Fibreglass is costed (in large part) by the weight of the materials that go into the particular object that is being manufactured and, if you're using anything but gravel, being able to get away with half of the media is a further significant saving.

The 300mm thing is one of those "guidelines" that someone suggested early in the piece and (like many other things around aquaponics) it's been accepted without much question.

The fact is that tomatoes will grow happily in no media and corn is a plant (like root crops) that wouldn't survive a cost benefit analysis as an AP proposition. Just about everything else will grow in 150mm of media.

Some of the other benefits of 150mm grow beds include portability (important for those who rent their homes) and ease of maintenance and cleaning.......and despite what people currently think, all growbeds will require cleaning sooner or later.

Gary

[Dufflight]

Wouldn't it be cheaper to get one 1m X 1m X 600mm
than two 1m X 1m X 300mm because you only have to pay for one bottom. Think it depends on space and FT volume. If you only had room for a small gb but need more media for bacteria then deeper is the way to go. Just another variable.

[Outbackozzie]

Points taken Gary