Backyard Aquaponics
A place to discuss aquaponics

Newbie Question - I just finished reading "Aquaponic Gardening" by Syliva Bernstein. It was really great !

Anyway the systems in her book have media beds and the bacteria live there.

So my question is, in systems with 'floating beds' and no media beds where does the bacteria live ?

Also, in a Floating bed system, would it be beneficial to also have a media just for the bacteria ?

Thank you,

~X

In case the image did not attach to my previous reply, i will post link to the photo on Flickr :

https://flic.kr/p/MAwkFJ

AP_Hybrid_Idea by Kevin Carpenter, on Flickr




These links are all to the same photo - hopefully one of these will work.

Thanks,

~X

I am hoping to learn from others who have invested thousands of hours and probably thousands of dollars in AP.

The purpose of our AP system will be educational, though we will also enjoy the fresh food !

Thank you,

~X

Hi ~X,

Welcome to the BYAP Forum!


Good questions!

The bacteria live in the water column (swirling around in the water itself) as well as all of the surfaces -- so in a DWC system that means the bottom of the rafts and the sides and bottom of the trough and roots. Also it is common in DWC design to have external filters to get rid of solids as well as an external bio-filter (like MBBF with K1 media.) Your design with the combination media bed and DWC is a nice one. You might consider not using a siphon in the media bed and just go with constant flood so that the DWC has a more even water flow rather than receiving water in giant spurts. But that looks like a very workable design. The constant flood (CF) will also help maintain the water level in your fish tank.

Good luck!

--
Sam

Thanks Sam,

Here is an update :

https://flic.kr/p/MADHt6

AP_Hybrid_Idea_2 by Kevin Carpenter, on Flickr


~X

Here is a link to someone else photo on Flickr :

https://flic.kr/p/e3hQ7a

There are a few people doing it the same way as you. It'll work fine.

Good luck!

That all works well if it is something like this below... (small example, but scales up)
This example could easily have 3 or 4 DWC tubs to the one media tub.
It goes from fish tank at bottom, into media tub and then passes out through a pipe to the DWC tub.
And then out of the DWC to fall back to Fish Tank.

In an AP sense you would need enough media volume to balance the number of fish.
If not being used as a grow bed the media tub/bed can be deeper as long as Dissolved Oxygen DO stays reasonable.
Can even be a media filled drum.
it is mainly submerged surface area of media you want to host the bacteria.

Note sure about you figure/sketch but normally you wouldn't come up from bottom,
just go over side for the pump discharge. You can put it down to bottom
or just have inflow outflow at different parts of media bed/drum/tub.



You can use polystyrene floating raft but then may have to consider having air in the DWC as roots need air in that type of setup. The picture above uses the Kratky air gap approach - so light acrylic cell roofing sits on top of tub with a few centimeters (inch or so) down to the water. Baskets can be media filled or can use plastic foam.

Thanks everyone, I'll let you know how it works out.

Which is better for the bacteria in the media bed, a 'fill and drain' cycle or keeping the media bed flooded ?

My reading promotes 'fill and drain.'

I was planning on a timer pump and smallish holes at the base of the stand pipe in the media bed. The effect being that once the pump stopped the water in the media bed would completly drain out those smaller holes and draw O2 down into media bed.

But now I am wondering which is best ?

~X

~X,


I think the general consensus on that has sided with the BYAP Trials doing side-by-side experiments: BYAP Trials.

It's a tie. Constant Flood or Flood & Drain -- the end result was that they both worked equally well.

Of course more experimentation is always welcome! Configure your system where you can do either/or and then if the bug bites you to take a walk on the wild side, you can switch!

There are many fans of CF about these parts!

--
Sam

it is not about what is best - as Sam notes it can be a tie as in case of the BYAP trials - though there are some subtle differences that EB notes in that trial thread. It is about making sure that any system maintains the maximum opportunity for bacteria to thrive. Aeration and water replenishment is a major factor - but it does not have to be done every 15-20mins (ie. a siphon) and can be done at much lower thresholds. It is also highly dependnet on the number of fish that are being dealt with.

The example above was done on a timer with pump running 30min-30min and only a small drain - not total volume. But the water was being removed from the bottom by a drain pipe to waste once a week (used to water pot plants and wicking beds) and the DWC was flushed multiple times in each cycle.

By having any form of flood and drain you are basically making sure that the water is being replenished.
In many systems you can do this once per day or even once per week. A good continuous flood needs to pay attention to where the water comes in and how it goes out to ensure that the likelihood of pockets of stale water do not develop. *IF* water is being turned over it does not matter whether you drain or not.

To address the water fluctuation aspect it is possible to only partially drain the grow bed / media bed in each cycle. So set the drain to take out say 30-50% of the water in an off cycle. That way you get some root aeration benefit and the new inflowing water promotes some displacement of the left over water in the bed (if in-out flows planned sufficiently). You can do this by having the standpipe drain hole a bit higher up - and you can have a couple of different standpipes to suit different stages and water level needs.

IMO the biggest issue is system design rather than method/s you choose to use.

Hi Guys,

with the two different types of GBs in the one system does the single water flow rate benefit one system more than the other?
I was thinking with F&D on a timer in the gravel bed 15/60 would flood and overflow nicely then drain and draw in the oxygen to say 50 mm off the bottom. If it takes 60 min to drain is that flow rate too slow for the DWC or would it benefit because there'd be less current to wipe nutes off the roots?

Pete.

not really sure, but DWC's do need a more regular turnover of water than a media bed.
You don't drain a DWC so rely on flow to do the replenishment and bring in aerated water.
In most DWC's if you took the rafts off the flow would not really be visible - very gentle.

The media bed wont really care. You already have anything from 15-20mins (siphon) to being static flooded for periods of time - so the DWC would be bigger consideration than the media bed. Mostly system flow rates are for the benefit of the fish tank rather than the veg..

in a big DWC people often run air anyway, so local air turbulence would exceed flow turbulence.

with DWC I would probably be running the pump more frequently.
mine run on 30min-30min for example. and many would have constant flow.

[edit] even in normal timer F&D you don't really want a prolonged slow drain.
usually you drain out a bed fairly quickly 10-15mins or so , if not quicker.
too small a hole has risk of blockage anyway.
there is also the issue is making sure that bed moisture levels are sustained - esp. in hot weather.
BYAP go with 15-45 as a default, but many find bit more helps with fish tank aeration & circulation.

Three examples come to mind here...

Friendly Aquaponics likes 5 GPM / 19 LPM:

Water Pumps And Flow Rate In The Vegetable Troughs

In UVI's standard system they adjusted water velocity based upon fish capacity up to 100 GPM / 378 LPM:

UPDATE ON TILAPIA AND VEGETABLE PRODUCTION IN THE UVI AQUAPONIC SYSTEM

But note their dimensions...

The 3rd example is from Andrea's Garden... One of the last changes well-respected dasboot made before he had to put aquaponics on hold, was to decouple Fish from Plants. At that point, he slowed down his DWC to turning over twice per day...

Crappy Basil Growers R Us, page 122

Bottom-line seems like more experimentation might be able to provide a more conclusive answer. I think most folks base their water flow rate more on what is best for the fish than the plants. I don't think you'd have to worry about "wiping nutes off the roots" as long as you weren't extreme about it (like the fire-hose keeps breaking off the roots!) because there would always be more nutes coming via the passing water...

--
Sam