Raft vs. Media filled Grow Bed (Sustainability)

[James McCullough]

Lots of people seem to advocate an Ebb & Flow system for hobbyists and a raft or DWC system for larger commercial applications. So what's wrong with a large scale E&F system? Okay so the media could get expensive, solids loading may be too intense at large scales and the total ratio of fish weight to system water volume is lower.  However, in favor of Ebb & Flow is the potential for greater mineralization of solids to provide more and different kinds of nutrients (supposedly eliminating the need for nutrient supplementation), better electrical efficiency by reducing active aeration requirements to the hydroponic/nitrification side of the system along with non-continuous pumping, the elimination of clarifiers and degassers and potentially better water usage efficiency (water required to handle solids from filters/clarifiers vs. lower evaporation rates in raft system).   Has anyone tried or considered a commercial sized system that uses a 0.5 lb/gal fish to tank ratio (at max) and just increases the tank to bed volume from 1:2 to 1:3 or greater?  Seems like if you kept the plant to fish ratio the same while making such an increase in bed size then this would handle the issue of solids in a large E&F (just till thoroughly between harvests and keep up the worm population in the bed). Any thoughts? I'm trying to design a system that uses primarily solar power and collected rainwater while still being scaled to a small commercial size, so an effective E&F system would be ideal if possible.

[Richard Joseph]

Quick qestion - albeit slightly off topic...

Could one use glass marbles (partly or entirely) as a grow media or have I simply lost my marbles?? I ask because gravel is very heavy...

[TCLynx]

Glass marbles are going to be fairly heavy too and probably far more costly as well as being really smooth so they will provide less surface area for the bacteria but the biggest issue with marbles will be that they will let light down deeper into the grow beds and thus not be so good for roots or bacteria growth.  Otherwise they could probably still be used.

Now there is a light weight media made of recycled glass called growstones, looks a bit like lava rock.

[George]

What about a small, proof of concept, hybrid system?  You could start with fish tank and media beds and then add from there once you are cycled up.  I would think that you might possibly need a year or so to prove concept but maybe you can do it in less.  My hat is off to you.  I hope to be involved in such a project myself someday so I'll be following this closely.  My system runs off solar but during overcast days I'm supplementing from the grid.  What I'm thinking of trying next is running aeration from solar, 24/7 but pumping from tank to beds with grid power.  Then, during power outages, I'll run entirely from solar, with a reduced pumping and feeding plan until grid power is restored.  Good luck.

James McCullough said:

 would you suggest that I try to convince him to start with a small media bed setup as a proof a concept and learning experience and then proceed to move to a hybrid setup? No matter what option we go with, we'll be recording a TON of data and I look forward to sharing the results