Backyard Aquaponics
A place to discuss aquaponics

Excess Nitrates?, you can run with pretty hi readings of nitrates, unto 180-200 ppm off memory. if you have more than that you should really be looking at your stocking density and or quantity of GB's or plants in them.
The filters are more solids removal, and if you can treat them and get them back in the system then happy days, not wasting the nutrients. Solids are an enemy to DWC as they bind to the roots and cause nutrient lock out or something along those lines. Also settles on the bottom which can cause another set of issues.
Costs money to get nitrates into the system so don't see the point in removing/wasting them.

Can I ask how you filter now Dasboot?

There are 2 types of filtration, mechanical and biological. Mechanical refers to knocking out or filtering solid wastes by use of filters like radial, swirl, brushes, shade cloth ect. Biological refers to a filter using a medium for bacteria colonisation to convert toxic ammonia to reletively harmless nitrate, this would be a grow bed, bioballs, kaldnes etc.

A mechanical filter would colonise to a degree but that isn't its purpose and will require regular cleaning, this is where you would flush away some nitrates. A biological filter will only be home for the conversion and will do nothing to remove nitrates, this is the biggest problem in RAS because they need to flush filters or change out water. In AP we use plants to uptake the nitrate so water changes or flushing is not required.

If using a shade cloth filter to polish the final water before it goes into the DWC it will need to be cleaned regularly but don't rinse it under the tap, wash it in the filter drum, aerate the crap out of it then let it settle and remove the solids then let the nutrient rich water back into the system.

The problem i had was there was so much shade cloth in the 200 litre barrel,although doing a fantastic job of polishing the water,it was a F…in nightmare to clean and just not a nice job everything including myself got soaked.Filtration now is by taking the water from the surface of the fish tanks then passing it through a 60 litre barrel loose filled with Bio Balls,the surface water contains practically no settleable solids and what is in this feed the BIo Balls handle very well,daily i open the bottom drain and the crap that has settled out in the bottom just goes to waste. Weekly i empty the bin and back flush with a hose,i think i could actually go two weeks between cleaning.
The difference in the system between the two types of filtration is my Nitrate level has gone up,i was at zero now its 10/12 ish so i am happy with this.
Charlies explanation in the last paragraph also shows why it isn’t the best way to do it,its just plain dirty hard work.

I a Agree 100% Dasboot, cleaning the shade cloth was a regular pain in my butt. For that reason I probably shouldn't have suggested it. Dasboot has tried many variables so I would take his advice on this one.

I got the hint from, A reading about the UVI system, B,then having it confirmed by Ryan in his back yard porch system,Ryan had a shade cloth filter and he clearly states his cleaning regime would be by the Nitrate level he wished to have for what he was growing. So with this in mind when i had poor growth in the DWC i worked it back to the filter and my cleaning regime leaving me with no Nitrates,but a 200 l barrel full of shade cloth is just a pain in the arse to clean,my new version is far more user friendly cleaning is down to 10 mins and on the up side there isn’t a build up of solids in the bed.
Most probably the nitrate issue was not the only reason,but having now eliminated it and have a nitrate reading i can tick this off the list and look in other directions if i have a future problems.

PLJ, if you are using the shadecloth it as a biofilter you wont loose nitrates. If you are using it as a mechanical filter that needs to be cleaned you will be loosing nitrates and nutrients. By the sounds of it dasboot has his system very close to balanced. If you are already running a higher nitrate number, you would loose much in the way of growth i wouldnt suspect.

I am glad that got cleared up; I was getting a bit worried that newer members would think that aerobic biofilters would reduce nitrates to any significant effect.

Yes, sorry now looking at they way i wrote that its almost half an explanation and could be very misleading.

Hey Charlie.

Sorry for loading you up with questions lately.
The wood used to make your grow bed, did you use marine ply or just a structural ply?
Treated pine for the frame?
I can't weld so will make the legs wooden as well.

Is the DWC worth it for a beginner or would I just be better off with media filled?
I have a food grade IBC that i want to make into a second system for silver perch so I have something for the main tank when the trout come out but can't do all at once.
Money is kinda tight at the moment and it looks very likely I will be made redundant shortly. Federal budget has ended the Biodiesel industry in Australia by the looks of it. So much for trying to be green..

Redundancies are popular everywhere this year hey. We have lost a lot of good people at the mine that I work at and its going on all over the place. Even Channel 10 layed off 150 people the other day I read in the paper. Sorry to hear and I hope you make it out the other side mate.

I used treated pine for the framework and chip board for the sides and bottom. I only used chip board because it was fee but Id recommend using a ply wood. I used a timber oil that I had in the shed over the entire thing before the liner went in but I did notice the weather started degrading the coating so Id shop for a good wood sealant to prolong the life.

I think a DWC is worth the effort to set up, you will learn many things from it and it smashes out the leafy greens. If your on a tight budget it would be cheaper for you to turn an IBC top into a DWC, similar to the one that was posted today. It doesnt give you a lot of growing area compared to making a long raft but it will be cheaper to build, especially if you already have the IBC.

Food for thought anyways.

I want to keep the IBCs for a fish tank and rainwater tank

I can see this costing somewhere around $500 (plus pump)
I'm fine with that.

Is it just held together by nails or wood screws?

Cool, cool.

Wood screws and wood glue. There are some photos in the thread somewhere what the frame looked like when screwd together before the boards went in.

Charlie, have you started setting your new system up yet? I just read flicked through the photos of this thread and was very impressed with the success of your system!!


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Or do I bite the bullet and buy this?
http://www.gumtree.com.au/s-ad/murdoch/ ... 1048257301