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Comment by David Schwinghamer on March 1, 2012 at 8:34am

I think you are doing something similiar to what Im doing, its called Chop 2 from Murray Hallam of Austrailia, you probably already know that. The filter in the sump is not what I have, Im assuming that is for solids? I actually am using three ibc totes, one for fish, one for sump, first two hydroton beds that siphon into a center raft bed then back down into the sump. I would think all you would have to worry about when adding would be the size of the pump. Its much better to go too big than small because you can always regulate the water with inline valves, happy growing!

Comment by Elizabeth on February 25, 2012 at 10:14am

Thanks again for the feedback.

Here are my design criteria:

1. Small media and raft tanks on the order of 4' x 4' x 2' high, max.  Rafts and media tanks all the same size.  I can fit something this size in my SUV and can carry it by myself with no assistance.  I can also build wood structures to hold them. Using multiple small tanks also gives me a lot of flexibility as to how I arrange the tanks.  I was thinking that I would start with one of each kind of tank, but if things go well I might eventually expand to five of each, or maybe even ten. 

2. Fish tank on the order of 2x to 3x the media tank size.  It will be initially to support a 1:1 media/raft:fish ratio.

3. Sump tank - this enables me to keep the fish tank at a constant level.  It also lets me incorporate additional fish tanks into the system by dumping into the same sump tank.  Again this lets me keep the fish tanks small enough that I can carry them and move them around.  It also lets me use one pump, which reduces the number of possible failures in the system.  I added a float valve with a chlorine filter to the sump tank to compensate for evaporation. 

4.  The reason for the sequencing value, which I'm not sure I need, is that I can't figure out how to evenly distribute the water between multiple small media beds using a single pump.  If I just use one pipe with multiple outlets to each bed, then the first bed will get a lot of water, and the beds further down the pipe will get less and less.  This way each media/raft bed essentially functions independently and I if they are all the same size I can use the same pump time and flow rate to flood each bed.

So the key design criteria are multiple beds, multiple fish tanks, and one pump for maximum flexibility and minimum failure modes.

Thanks again for all your thoughtful contributions.

Comment by Rob Nash on February 25, 2012 at 8:58am

they say "a farmer must possess more skills than should be expected of one person"

in AP plumbing is everything. Without a floor plan or an idea of your tank size, etc. its difficult to walk you through it. but you will need to plumb the line to split to each bed.

the polisher is to remove the last of the solids that the media missed ...keeps your raft water clean ...it is not a must have, but IMO, its highly recommended.

most systems can be expanded on, but i feel its better to build a complete system, (in terms of - beds and tank ratios) and then build a new one each time you want to expand.

 

start with a 300 gallon Rubbermaid water tank ...build your beds out of plywood and 2"x12"s and liner.

for this tank you can have two 4' x 8' beds (32sft) for a total of 64 sft of media, and if you want to add rafts you could do 128sft of rafts

 

Comment by Elizabeth on February 25, 2012 at 8:38am

Thanks for all the feedback everyone.  It is really helpful. I want to avoid as many mistakes as possible before I spend any money or time.  I also want to make the system as expandable and flexible as possible, as I am hoping to make more and more.

Rob, can you tell me what the "polisher" is?  Also, can these two systems be expanded to have more than one media bed and raft?  How do you distribute the water from the fish tank equally between additional media beds? This is why I had the sequencing valve, but if I don't need it then I will happily eliminate it. What is the best kind of siphon to use - bell?

Thanks,

Elizabeth

Comment by Rob Nash on February 25, 2012 at 7:07am

Im with Rupert and Carey, go with constant flow and bell siphons, let go of the indexing valves and the filters.

I dont think a sump is necessary if you have the correct FT to GB ratio.

Add an air pump in the fish tank and rafts.

...here is a drawing of an overflow system, using the raft for the sump.

 

 ...this one has the media bed on 3 blocks and the raft on 1 block, which makes the water level in the fish tank and the raft the same. ...the raft overflows back to the fish tank. you may need to dig the fish tank into the ground 6 inches.

 

 

Comment by George on February 25, 2012 at 5:40am

Will you be able to comfortably work your media beds?  How high do you expect your planting surfaces will be?

Comment by RupertofOZ on February 25, 2012 at 3:46am

Timed flood & drain, with an overflow standpipe would be a necessity if utlising a sequencing valve....

But IMO.... a constantly pumped... constant flood system would be optimal.... both for the media beds, and for constant flow into/through the rafts...

Comment by RupertofOZ on February 25, 2012 at 3:43am

Vlad, "rushes" of water through a raft... from siphon initiation... may well work... especially if the siphons were fast fill/fast drain.. multiple turnover/hr...

My concern would be maintainence of DO within the rafts... particularly in warm weather....

Too slow an inflow rate.. could result in DO depletion.... and depletion could/would be exacerbated by warm water, which inherently holds less oxygen....

 

Root rot would be my primary concern...

Comment by Carey Ma on February 25, 2012 at 3:24am

Other than what Rupert wrote, I don't think filters are necessary if you are using the media beds as your filter/ bio reactor.

Comment by Vlad Jovanovic on February 25, 2012 at 1:19am

Rupert, just out of curiousity...why do rafts need a water to be in a constant flow? I'm thinking of people like Chris Smith from Coastview AP who have a similar set up where his rafts get water in "rushes" when the media bed drains. I believe he's been running part of his set up this way for well over a year now with no big complaints? 

Though really, I'd probably connect the rafts and have all of the media beds drain into the first one. (Thus giving a much more closer to constant flow scenario to the rafts). I have all 8 of my media beds plumbed in just this way, so that when the indexing valve is doing it's job, a pair of beds will always draining, while another are filling etc...

And would never use siphons with a sequencing valve, it's unnecessary and begging for trouble. Timed flood and drain seem the way to go with that type of device. (Stand-pipe with a couple of small hole in the bottom, and a decent repeat cycle timer, replacing the siphons).

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