Backyard Aquaponics
A place to discuss aquaponics

hello there people of the earth.
this is fun. thanks for this site.
i a noob so bear with me here.
say i wanted to grow lettuce in a deep water culture method, say in a 2x3m cement dam above ground, lined ofcourse(with what?)
how many fish would i need if if i decided to do a run of system of 3 such dams flowing into each other? would this even work? i couldnt find anything on dwc on the forum yet.

God bless.

Welcome Daniel

Hi Daniel,

First off, not everyone on this forum claims to be from Earth (I suspect they are in denial) or even
to be "people" in the normal sense. But generally we seem to be a pretty good crowd of folks drawn
to this weird idea of mixing gardening with fishing...

Using the Search function of the forum (Search box in upper-right corner of webpage):
works pretty well. It should find almost 5000 mentions of "dwc" in the forums (including yours!)

I believe most folks that line growbeds do so with plastic liner. How thick the liner should be does
sometimes come up. Several have used liner that is too thin. If you are not putting this in the dirt,
you probably don't need something as thick as normal pond liner. I have yet to line a growbed so
others could chime in better than I about liner thickness. For me it more often comes down to using
what I can get. Colum's got a nice video about using a liner in one of his build videos. In the video
he mentioned "about 0.4 or 0.6 mil thick", but I suspect he meant 4 mil or 6 mil thick. Americover,
who sells "aquaponics liner" recommends "12 mil and 20 mil Reinforced Polyethylene Sheeting"



Aquaponics using the DWC method is usually not considered the easiest thing for a noob to attempt
in part because it typically involves more advanced aquaponics systems with 1 or more filters and
there are more technicalities to be on top of than if you were using a media-based growbed. But
more power to you, I say. If you've got the ganas to do DWC, go for it.

Good luck!

--
Sam

Hi danielf12,i run two 9x1.2x.38 metre DWCs,these are built from concrete blocks lined with a plastic liner,i used the plastic they use for green house covering here,if you go to my thread you can see how they were constructed.
DWC requires adequate filtration before to capture solids before they get to the troughs,this could be in the form of an RFF leading to a fines filter of maybe netting or similar,with enough aeration within the trough your bio filtration will be taken care of within the DWC.Turnover needs to be once per hour to once every two hours,so if you work out the capacity of your troughs this will give you the fish tank size requirement working on fish tank turnover of once per hour.
Stocking levels,with three troughs you have approximately 18sq2 off grow area and there is a figure quoted of this being able,with the correct aeration to deal with 180 grams of feed per square meter of grow area,which is a large amount,so depending on what fish your using,i use Tilapia which are fed 1% body weight per day,when you finalise your design you should be able to work out your figures from there,these will be maximum amounts which as a beginner you wouldn't want to stock.
I would have the three troughs as three individuals,this way when it comes time to harvest or clean you can isolate the individual trough to do this without disturbing the entire system.In my system my DWCs are over twice the volume of the fish tanks,so to ensure enough nutrients for the system i utilise a mineralisation tank where solids from the RFF are put on a daily basis to capture as much of the nutrient value as i can,this is something you could think of using as it will allow you to have a lower stocking making it more user friendly for a beginner,but still achieving the nutrient level you need for the system.
I dont know if this is helpful or confusing for you,but any question just ask.

Builders plastic is 200um (or.2 mil) so I seriously doubt Column meant 4 to 6 mil.

Sleepe, this seems to be location dependent. In my area, there is code requirement for 6mil vapour barrier, so that is pretty much the lightest that is readily available. I think I'm going to try it as GB liner when I get to building them, but I'm not committed yet.

The plastic i use was .15um,using the polystyrene as an insulator and protection for the liner.

Okay, surely we are talking about different definitions of "mil" here. 200 um is 200 micro-meters, as in microns,
as in millionths of a meter, right?

http://dictionary.reference.com/browse/micrometer
micrometer mi·cro·me·ter 2(mī'krō-mē'tər)
n.
Abbr. μm A unit of length equal to one thousandth (10- 3) of a millimeter or one millionth (10- 6) of a meter. Also called micron.

http://dictionary.reference.com/browse/mil
mil
noun
1. a unit of length equal to one thousandth of an inch

So your definition of "mil" is thousandth of a meter, i.e. millimeter. I didn't know that was a common definition -- I use millimeter (mm) for thousandth of a meter. When I see "mil" I think milliinch as in thousandth of an inch. So when I see 200 microns (or 200 um) I see almost 8 mils (7.87 mils). I'm sure when Americover recommends 12 mil or 20 mil liners they mean milliinches not millimeters. 1 mil = 25.4 um so then Colum's 0.4 - 0.6 mil (millimeters), or 400 - 600 microns, converts to about 16 - 24 mil (milliinches.)

I see some Australian pond-liner companies using millimeters like "0.70mm and 1.0mm" or "1.14mm and 1.52mm thick".

Makes sense now. Thanks for the enlightenment!

--
Sam