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Hi All,

I'm planning for a system with roughly 100 sq. ft. of growbed area, and am considering the choice of purchasing individual beds or making them.  If I make them, they can be any size.

 

Obviously the plumbing would need to be the appropriate size to flood and drain each bed, and I don't know what the practical limits of a bell siphon would be, but are there other downsides to having a large media bed?

 

Would 4x8 be too large?

Thanks,

Paul

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Hi Paul, I'm building 3 media beds that are 4 x 8 ft. I'm experimenting......To start,  I'm trying a 1 inch drain, with an Affnan bell. I'll be trying two different size stand pipes....1 x 1 1/4 inch and 1 x 1 1/2 inch.

The water amount in the bed should be around 100 gals.   I know one inch sounds small....I'm trying to keep the pump size/water flow small, to save on electric. The Affnan bell,  should help with the smaller inflow of water.

 

Here's a PDF you may want to check out. It does have a chart in it,  showing the bell sizes they recommend......

http://www.ctahr.hawaii.edu/oc/freepubs/pdf/BIO-10.pdf

 

If you notice, they are using 'standard bells'. The 2 " stand pipe, they recommend, would take a 'large' pump/ large inflow to make it engage.

I'll keep you posted.



Hi David,

Thanks for that pdf link - that's a great resource.

 

The Affan bell seems more elegant in design as you don't have to deal with a snorkel tube.

Hi Paul
I build my own 2mm liner grow trays..Cheaper and like you say they are build to suit your layout.
I am very happy with my trays…

folded end

 

 

from inside

 

 you can make as deep long and wide as you want
these grow trays are 180 high and 6500mm long
i would keep them narrow and if you go deeper add support along the sides 

 

 

Hi Francois,

Those look quite strong and tough.  This is for a siphon type system?

Can you share your source for the material?  Do you know if it's food-grade?

 

Thanks!

Paul

I have some experience with very large grow beds.

 

First, think twice before building a wood and liner grow bed, especially if you live in termite territory.  I only have one lumber/liner grow bed left to replace and that one was built using treated wood.

 

The Largest grow bed I've done was about 28 feet long and 30 inches wide by about 14 inches deep.  The flow through the media becomes very critical and trying to do some form of autosiphon or even a float switch on a pump installed in one end of the bed will depend very much on the flow you can get through the media itself.  This is where the Larger media recommendation becomes rather important. 

 

Also, keep in mind that constructing a very large grow bed and keeping the top edge perfectly level and keeping the sides from bowing out will be pretty important.  If you have a really big grow bed and it doesn't stay level, you might have one end with water washing over the top edge while the other end isn't flooded deep enough to trigger the siphon do do your construction well.

 

Dollar for dollar, I've found the 100 gallon stock tanks to be really great grow beds.  They cost only a few $ more than the 50 gallon version and you don't have to build a strong stand to support them since 5 concrete blocks will take care of it.  Instead of trying to get siphons to work, I've been just using the gravity modified indexing valve and a 50 watt pump to sequentially flood and drain the six 100 gallon grow beds hooked to my 300 gallon stock tank fish tank.  Water level in the tank barely fluctuates and the filtration is rock solid even while I have probably way too many fish in the tank and yet by growing greedy plants like corn and tomatoes this summer I have the Nitrates running only about 5 ppm even with the deep grow beds providing less planting surface than the normal 12 inch deep beds.

 

Now that plastic seet that Francois uses, I've gotten some of it and tested it for some things but you will need a fair bit of support to do 12 inch deep beds with it.  You can get it in food grade, it's just HDPE plastic.  I see it as a good choice if you will be placing the troughs directly on the ground and can provide strong supports for the sides.  If you have to elevate it, you will have much cost in building the support for something to hold gravel.  I'm currently using it under my towers to make a long narrow sump tank with the edges supported by fence rails.

Wow - 28' x 3' now that IS big.  Yes, I can see the water flow through the media as being an issue... I guess that was one of the nagging issues I couldn't fully identify verbally.   And the leveling as well.   I appreciate you mentioning the termites and the other physical challenges too.

 

My goal in making the bed as large as possible, would be to eliminate as much plumbing as possible.  Do you know off-hand the approx. sq. footage of your 100gal stock tank?

 

I believe I've read before that these Rubbermaid black tanks are not food grade, but are the next best thing?  Is there a recycling symbol on them? (to determine material)

 

Thanks!

TCLynx said:

I have some experience with very large grow beds.

 

First, think twice before building a wood and liner grow bed, especially if you live in termite territory.  I only have one lumber/liner grow bed left to replace and that one was built using treated wood.

 

The Largest grow bed I've done was about 28 feet long and 30 inches wide by about 14 inches deep.  The flow through the media becomes very critical and trying to do some form of autosiphon or even a float switch on a pump installed in one end of the bed will depend very much on the flow you can get through the media itself.  This is where the Larger media recommendation becomes rather important. 

 

Also, keep in mind that constructing a very large grow bed and keeping the top edge perfectly level and keeping the sides from bowing out will be pretty important.  If you have a really big grow bed and it doesn't stay level, you might have one end with water washing over the top edge while the other end isn't flooded deep enough to trigger the siphon do do your construction well.

 

Dollar for dollar, I've found the 100 gallon stock tanks to be really great grow beds.  They cost only a few $ more than the 50 gallon version and you don't have to build a strong stand to support them since 5 concrete blocks will take care of it.  Instead of trying to get siphons to work, I've been just using the gravity modified indexing valve and a 50 watt pump to sequentially flood and drain the six 100 gallon grow beds hooked to my 300 gallon stock tank fish tank.  Water level in the tank barely fluctuates and the filtration is rock solid even while I have probably way too many fish in the tank and yet by growing greedy plants like corn and tomatoes this summer I have the Nitrates running only about 5 ppm even with the deep grow beds providing less planting surface than the normal 12 inch deep beds.

 

Now that plastic seet that Francois uses, I've gotten some of it and tested it for some things but you will need a fair bit of support to do 12 inch deep beds with it.  You can get it in food grade, it's just HDPE plastic.  I see it as a good choice if you will be placing the troughs directly on the ground and can provide strong supports for the sides.  If you have to elevate it, you will have much cost in building the support for something to hold gravel.  I'm currently using it under my towers to make a long narrow sump tank with the edges supported by fence rails.

In your figuring, just make sure you are not stepping over dollars so you can pick up the pennies.  As in make sure that by saving on a few plumbing fittings that you are not spending a lot more in making a big bed.

 

Square footage of a 100 gallon stock tank, duh.  Since it isn't a rectangle it is hard to give accurate square footage.  I've usually done my system ratio figuring based on filtration volume compared to fish tank volume and there fore the 100 gallon stock tank beds are really easy on my method of figuring.  The stock tanks top dimensions are about 31" by 53" but it is kinda an oval sort of shape so it's gonna fall short of 12 square feet of planting space.

However, since the beds are double deep, you get lots of filtration so if you were to find you needed to add more plant space due to abundant nutrients, it would be a fairly easy thing to add a raft bed fed by the drains from the deep grow beds to provide more plant space should it prove necessary (so far it hasn't been needed in my 300 gallon system even with a probably too big fish load.)

And while I DO NOT recommend lumber and liner for a gravel bed anymore.  A raft bed will be far easier to patch should you get a leak and the lack of gravel means the support structure of the bed doesn't have to be quite as strong to avoid bowing and by using a radius in the bottom corners of the raft bed the liner will actually pull down on the supports rather than pushing out.  Flood and drain gravel puts far more stress on a container than just water.  Water is heavy but the combo of water and gravel is extreme.

 

Are stock tanks food grade?  Well I've not seen a food grade stamp on them but they are definitely feed grade (I have no qualms about using the rubbermaid stock tanks whatsoever) they are made of HDPE structural foam plastic and the Ladies at Green Acres use them and they make sure all materials would be acceptable for going organic.


Paul Braun said:

Wow - 28' x 3' now that IS big.  Yes, I can see the water flow through the media as being an issue... I guess that was one of the nagging issues I couldn't fully identify verbally.   And the leveling as well.   I appreciate you mentioning the termites and the other physical challenges too.

 

My goal in making the bed as large as possible, would be to eliminate as much plumbing as possible.  Do you know off-hand the approx. sq. footage of your 100gal stock tank?

 

I believe I've read before that these Rubbermaid black tanks are not food grade, but are the next best thing?  Is there a recycling symbol on them? (to determine material)

 

Thanks!

All very good points TC - added filtration and a built-in stand.  And you have 6 of these with your 300gal FT. 

Is the FT rubbermaid 300 gal one?

Here is a blog post Video of it from last Jan

300 gallon system

 

Yes it is a 300 gallon stock tank, though I feel that is a touch shallow for a fish tank for some types of fish.  Seems ok for Bluegill so far though.

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