Backyard Aquaponics
A place to discuss aquaponics

Hi Ladies and Gents,

I wish to add another DWC at home and wanted to know what depths others run their DWC or raft systems. My current one is 600mm deep but am not seeing great results yet and plants look very nutrient deficient even where the roots are quite clean. (I have the input coming off the drain from the GB).

Anyway my thoughts are to DWC depth. What works well so that when I filter correctly, get my air levels even and right, and then make the ideal depth unit.

Also, any recommendations on a flow through rate. i.e should I be turning the water over every hour... more or less?

Any assistance always greatly appreciated.

Dunno if anyone has done much in the way of experimenting with different depths running side by side to compare growth...

Our system was about 30cm all up, so water was probably only 25cm deep when the system was full, and down to 20cm when the water levels were a bit low.

Thanks EB. I found another site Aquaponic Garden Community where one of the members is doing raft style with an air gap between netpot and water.... doing away with the polystyrene and using 'polywall' basically looks like a flat sheet of plastic on a floating pvc pontoon. Anyway he likes the results as the added oxygen seemed to be assisting growth....

Everything else I have found is talking 12 inches or 30cm, so my 600mm is getting the chop!!

You never know though, perhaps there are advantages to extra depth?

We were about to do away with the polystyrene in our system and make rafts out of pvc pipe with corrugated plastic top like they use for signs, is that the sort of thing you're talking about?

Hope this it for you to see. All credit to original image owner. Put the web link underneath for reference.... sounds like you are doing the same technique perhaps...




http://api.ning.com/files/RUTrPA7URwoEyBLDVb8hyDa2wusPi8gWtgfGjjzyhrmnNQofxbTu-859Tbh*l4ELIyy9DhpsdFVYW6*6JFhLjJWCtRQSvkHS/CIMG2097.JPG

Yep, thats exactly the sort of thing...

Have a look here for a bit of a background read.

http://aquaponicscommunity.com/group/raftdeepwaterculturegrowers?groupUrl=raftdeepwaterculturegrowers&id=4778851%3AGroup%3A28261&page=2#comments

EB - Do you think the 'Corflute' of corrugated plastic is 'fish safe'? Haven't read up on it yet.

I don't think it kills fish, whether it off gasses other things that might not be good in the long term I don't know. I have seen commercial hydro producers that use it. Just goes to show, you never know what you are eating if you haven't grown it yourself. The same guy also used hardi flex sheeting and all sorts of stuff as part of his hydro systems...

Does anyone know why I shouldn't put a raft directly on top of an aquarium? I think you would need to ensure a good air stone with pump, but you wouldn't need a water pump. Perhaps the fish would eat the roots of the plants?

There isnt any problems with that. I saw one recently here but cant remember whos it was sorry. You just need to be weary of nutrient uptake versus stock level. If you are already filtering the aquarium then it would make a good addition.

This raft system might interest ...

viewtopic.php?f=18&t=13019

Part of the origanal post to this thread was about the flow rate needed through a DWC tank, can anyone give me an answer to this?
I'm planning on adding a full IBC for a DWC tank to my system, partly to add more water volume and help control water temp fluctuations to hopefully extend the trout season a little next year and also just to try something new.
my system atm is a timed flood and drain, so I was thinking of putting a second pump into the sump to pump possibly through an RFF then DWC and back to the sump, but unsure of how much flow I need?

Cheers for any help / advice you can give.

Ben

+1 to Ben's post!

I presume you guys found your answer about flowrate by now.
Seems the general idea is a retention time in the trough of from 1 to 4hrs.
So depends on the volume of your trough.
For example if you have a 300ltr trough, you want a flow rate between 5litres/min to 1.25 Litres/min. if my math is correct...which it often isn't.