Ebb and Flow BENCH Aquaponics

[Benjamin Casteel]

Good day, everyone.

      I recently became the greenhouse manager and an adjunct instructor at Virginia Highlands Community College.  Each summer in the greenhouse, Upward Bound students have an aquaculture project.  Last year, the previous Greenhouse Management instructor started an Aquaponics project in conjunction with the aquaculture project.  I appreciate his efforts in trying to create a more sustainable greenhouse production system, but I inherited a broken system.  We have about 50 nearly full-grown Tilapia in a 500 gal. tank which is cycled into a 35 gal. kiddie pool grow bed that is growing some MASSIVE tomatoes.  However, I'm sure you all see the problem here in the incongruity of grow bed to aquaculture ratio. 

     We do have the capacity to correct this with some Ebb-Flow benches that are in the greenhouse.  Here is a link to the manufacturer's website:  http://www.midgro.com/ebbflo.html 

     Does anyone have any experience or any advice in hooking up an ebb-flow table or any other sub-irrigation systems with an aquaponics setup? 

[Scott Roberts]

How deep are the sides on the ebb-flow table?  Are there metal pieces in contact with the water? You could use ebb-flow benches as shallow media beds, or put the media into mesh pots and sit them in there.  

[Benjamin Casteel]

The sides of the trays on the benches are relatively shallow at about 4 inches.  There are no metal pieces in contact with the water, just the plastic trays.  I would like to use part of the table space for seedling production for our class' spring plant sale.  One of the tables had a good amount of clay pebbles dumped in it and used for media to grow cucumbers in last year, but last year's course never used the fish water in the tables, so the cukes never got any fertilizer.  We will be continuing this project throughout the semester and need lots of help and suggestions!

Thanks, Scott! 

[Alex Veidel]

What kind of advice are you looking for?

[Benjamin Casteel]

I guess I am wondering if anyone has any tips or suggestions on the interface between that fish tanks and the ebb-flow benches.  Do we need any physical filtration before running a pump straight into the benches?  Or can we just go direct? 

We would like to use part of the table space for seedling production using soil blocks?  Will this work for water filtration or would it be more just used along the lines of sub-irrigation and fertigation? 

Any advice would be helpful :)

Thanks in advance!

[Alex Veidel]

On a home growing scale, it normally wouldn't be a problem. However, since your media beds are a little on the shallow side and since your fishtank is 500 gallons, it might be a good idea to install a settling tank to deal with any extra solids. Your media beds can handle a good amount of waste and you won't need a filter (unlike in a DWC bed). The settling tank would be more of a precaution (and probably an optional one at that, depends on what you want to run your stocking densities at). If you want to keep high stocking densities of fish, then go ahead and include a setting tank. One design I saw had a two pathways with a diverter. One path went through the settling tank before hitting the media beds and the other went straight to the media beds. That way you could control how many solids entered your beds at any time.