Monday, November 26, 2012

Filtering Poo with Continous Flow Media Bed

My indoor system started out with a gravel bed. After repairing a leak in the 45 mil EPDM liner of that grow bed, I decided to go with a Deep Water Culture (DWC) raft.  With only one 10' wall glazed my grow bed is 30"x10' long which is a rather small 25 sq ft..  I found it easier to utilize that precious space with a  raft system.
A panoramic view inside grow room.  800 gal fish tank on left grow bed on right

But loosing the large media bed meant that I would also lose the filtering capability of the 3/4" rock media.   So I decided to build a filter using evaporative cooler pads.   This works great at first, but after a few months the fish population began to grow and the fish got bigger.   The filter could no longer keep up with the poo.   Cleaning filters everyday was more work than I was willing to do.

So I decided to return part of the bed to a gravel media, and keep the rest as a DWC grow tank.

The DWC tank with gravel to the right of a plastic fence partition
I built a partition out of plastic fencing and PVC pipe.  Filled one side with 3/4" gravel and extended the return water pipe from the fish tank so that it dumps on top of the gravel.   One thing I'd like to say about that is I also used 2" pipe rather than 1-1/4" because the smaller pipe tends to clog.

At this point I began to have concerns about a continuous flood gravel bed.  RupertofOZ was kind enough to dispel my fears by pointing me toward a very good experiment done by  


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