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The results of this discussion will form the definition of Constant Flow Aquaponic Gardening on our Community Glossary of Terms. http://aquaponicscommunity.com/page/aquaponics-glossary-of-terms

So, how would you define constant flow based aquaponics in 50 words or less?  What are the advantages and disadvantages?

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Yes Sylvia... just as a timed Flood & drain system.. with a standpipe... but pumped continuously... and without the small drainage holes in the bottom of the standpipe... (which sets the height of the flood)...

 

This is the way that "ebb & flow" developed into "flood & drain" in hydroponics.... ustilised the same standpipe that was often added as an overflow/flood height in ebb & flow... but flooded from the top, rather than from the bottom...

The Hydroponic "flood & drain" usually incorporates small drainage holes in the standpipe.. to drain between cycles...

 

Aeration is usually acheived by the water return back to the tank/sump... as it normally is in a flood & drain system...

Often, and I recommend doing so... the tank/sump is aerated with an additional air pump...

So does that mean there is a constant level of water in a media bed - say 8 - 10" in a 12" media bed - that is always there and you just aerate it?

Yep simply a bed with stand pipe and no holes and pump to it constantly.  Extra aeration is provided to the water in the fish tank/sump tank and you need to make sure the water turn over in the bed is fast enough that the plants stay happy and the oxygen isn't depleted in the bed since it doesn't drain to provide the oxygen to the plants/bacteria.

Benefits of constant flood are that you don't have the water level fluctuation in the tank and water will hold a more constant temperature.

Drawback being the one about needing to make sure dissolved oxygen levels stay high enough to keep plants/bacteria happy and for most plants making sure the surface of the media stays really dry since there is no drying period for the plant crowns if the bed is being flooded too high.

Ricky, I'm going to use your definition from early on, but add in some language about the need for additional aeration...something like this

Constant flow systems have a consistent flow of water, as opposed to pumps on a timer or with timed drainage systems (bell siphons). The water comes in at a constant rate & leaves at a constant rate - keeping the water at a pre determined level.  Because oxygen isn't introduced by draining the beds, constant flow beds require supplemental aeration.

Let me know if you guys would change anything about this...I'm not a constant flow kinda gal so I'm still feeling a bit shakey about this one.

Again, constant flow needs more qualifiers.  Are we talking about constant flow flood of media beds or Constant flow of rafts, nft, towers?  And again, a siphon flood and drain system has a constant flow into the beds as well.  I don't believe the constant flood system over at BYAP has any additional aeration compared to the siphon and timed system in that same trial, they all have air pumps running.  In timed flood and drain systems I would normally recommend supplemental aeration of some sort as I do in most all systems.

Well, that is what I"m trying to get to  here.  There seems to be two different definitions, and the one I was honing in on is the one that makes more sense to me.  A siphon driven flood and drain bed is just that - flood and drain using a siphon vs a timer.  What matters, it seems to me, is that a bed would be constantly full of water vs drained.  I would think it is not about water always going into the beds - that is simply a technicality - but rather a differentiated style of growing that is where there is always water in the beds.  At BYAP are they doing what Ricky is doing...i.e. there is always a constant amount of water in the beds?

Here is a link to the thread on the trials over at BYAP

They have one system that is constant flow/flood (basically a stand pipe system, pump always on.)

Then another system is siphon flood and drain

Then the other system is timed flood and drain

But simply saying constant Flow Doesn't differentiate between constant flow/flood or constant trickle (or constantly flowing but drained) in a media system but it could also mean the constant flow in a DWC or a NFT set up.

Which is why I usually say Constant Flow/Flood when I'm talking about a constantly flooded media bed.

It really is quite simple....

A constant flow system.. regardless of whether it's a raceway, DWC, NFT, siphoned... or constantly flooded....

Are all continuously pumped...

 

Whereas periodic interval systems... such as timed flood & drain, ebb & flow hydroponics, wicking beds...

Are all interval pumped...

 

The only variations are variations of the drain cycle.... where siphons, are continuously, and usually fast draining... whereas interval pumped systems are usually slow, and periodically drained...

 

And DWC, NFT, constant flood systems... are effectively... never drained...

I think the important thing to remeber here is we are definig "constant flowñ and there will be (if i remeber correctly) definitions for NFT & DWC. Which means no need to worry about confusing them. Because we are giving a definition to the term, others won't be confused...it's only us, lol, who know the nuances of all these systems, that are getting stuck onsome of these technicalities.

I agree with Sylvia's pointthat the water input doesn't so much matter as the output. If the water going out is constant(whether its from a trickle, a standpipe, or some other method)and the level stays constant, then that is constant flow. There are always subsets of catagoriesand different ways to build systems (all of mine are constant but all are built a little differently)and those can bediscussed. But I think theimportant point is to get the main definition down so new comers can sift through information.

Well if we are saying that a "constant flow" system is not a DWC or NFT system then we should note that constant flow in this definition is for media beds and that would need to be part of the definition.

Also there is a huge difference in functionality to a constant flow Zipgrow tower compared to a constant flow media bed.

And the Constant flow media bed could have the same inflow and outflow but one version might be constantly drained with only a thin layer of water in the bottom while another is constantly flowing but flooded.  One version works great the other version not quite so well.  Constantly flooded and constantly flowing provides filtration to the water and water for smaller plants while the constantly flowing drained bed only works for the plants that can reach the water and it provides very little filtration.



Ricky Flickenger said:

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 I agree with Sylvia's point that the water input doesn't so much matter as the output. If the water going out is constant(whether its from a trickle, a standpipe, or some other method)and the level stays constant, then that is constant flow.
Sorry, but I think that's totally confusing, and could be totally wrong...

The difference for a continuously pumped, siphoned grow bed system... and an interval pumped timer/standpipe system... is considerable.. both in terms of water inflow... and outflow... and level...

Timed flood & drain with an overflow standpipe... doesn't have any inflow for possibly long periods, whereas continuously pumped siphoned flood & drain.. obviously has a constant flow...

Likewise... the levels of either don't remain static... and while the siphoned system could be said to (almost)always maintain some level within the grow beds... timed flood & drain could have extended periods of virtually no level within the grow beds...

And constant flood... will have both a constant flow... and a constant level... always...

I've never mentioned my growtower as a constant flood...I have 4 other filter designs running that are constant flow with media beds. I agree that adding media bed to the definition would be helpful as well, since, as I mentioned,I think DWP & NFT are getting their own definitions. If they aren't then I'd like to suggest they should as they are much different creatures.

You seem to have defined the difference between a flooded bed and a trickle again...I agree, as i just said above, that these are both "constant flow"...but I have been assuming we are goingfor a broader defintion here. If we try to define every different subset of different systems we couldn't do it in 50 words. My feeling is that the subsets can be discussed as being under that broad definition.

As for aeration, I thinkit is important to note the additional aeration is in the tank, not the media bed. Although my mature tankis currently running without any and is quite healthy - though is does have a good bit of flow/volume turnover.

This discussion is great!  Thank you guys for engaging with me in this as it is really helping to clarify some murky parts of my understanding of this.  I don't think we need to get into a lot of detail about the specifics, since we aren't doing that for any of the other definitions, but Thanks to Rupert's outline for how to think about this it seems that are are really talking about two separate definitions here - Constant Flow (vs Intermittent Flow) which defines the pump action, and Constant Flood (vs Flood and Drain) which is really a media bed construct where there is always a level of water and your water exits through an overflow vs a siphon or through timed action with the pump.  Can we all agree to this?

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