What's good on a raft?

[Louise]

I've got the cut-off top of my IBC fish tank, to use as an extra grow bed. For plumbing reasons, it seems easiest just now to use it for a raft culture rather than a media-filled one.

Question is - what plants enjoy being on a raft?

I have some squash/pumpkin plants that need space somewhere, but I assume they are too big for a raft, or not?

Lettuces?

What else?

[John Cubit]

I will be sure to let all my plants that are growing well and feeding us that they are  bad, unhealthy plants.  Especially those discolored ones...bad plants.

[R.K. Castillo]

Jason A, don't stop posting and trying to help people.  The guys in here can be real jerks sometimes (I have to admit I have secretly wanted some of them to come to Hawaii so I could punch them in the face!) but they help people...and a little heated discussion is a good thing sometimes.  It has revealed a lot of interesting info about what to do in DWC.  

So thanks for your conversation starter. 

[R.K. Castillo]

Thanks @Vlad  

Who do you think I should interview next?

[Vlad Jovanovic]

Yeah Jason, don't quit posting just because someone doesn't agree with you. A little bit of constructive mental sparring can usually help move things forward for both ourselves and others. I've got to say, I don't agree with you either...about agitation not helping somewhat to keep keep roots clean(er) or that an air space (as long as it's very high in the relative humidity department) is 'bad'...but that doesn't mean that you should quit posting...

I believe (at least in part) what Ryan meant when he said that it "wasn't up for debate", is that any single book/paper on soil science or microbiology as it relates to soil science, will pretty much confirm the premise that mechanical agitation should help to keep roots cleaner...from "gunk build up". "Gunk" being the technical term for fine particulate organic matter that makes it past your 'box-o-rocks' and/or conical filter/settling/net tank, or whatever your using for mechanical filtration and sticks to the polysaccharides that bacteria exude (technically called "slime"). The same 'slime' that clumps tiny, minute soil particles together into aggregates...also causes fine particulate matter to cling to our roots. That type of "gunk" really is broke up by agitation. Whether the agitation comes from a bass, a soaker hose, an air diffuser or (no one mentioned) flow rate...they will all likely do a number on the weak bacterial polysaccaride/"gunk" bond.

Now, that said...all the mechanical agitation in the world probably won't help much if the "gunk" at hand is oomycetic in nature...

These are probably the kinds of misunderstandings that (will continue) seem to arise when we use generic terms like "gunk", "good", "bad", "hot", "cold" and other meaningless and subjective terms etc...but the  "I'm taking my ball and going home" response probably doesn't really help to move the dialectic process forward any.

Having an airspace with high relative humidity between the top of your water and the bottom of your raft is a very common and prevalent practice in the soil-less culture world, both commercial and otherwise. There are many Kratky, or modified Kratky-type systems in use throughout the planet which utilize such an airspace...as the benefits have been studied, documented, and repeated by others many, many times...

@R.K. I'll be sure and not visit Hawaii anytime soon  (Great work on the pod casts btw...I really enjoyed them...thanks for bringing those to us all).

[Vlad Jovanovic]

hmmm...IDK the list in my head just keeps getting bigger...in no particular order:

Kellen Weissenbach 

Ryan Chatterson

Terri Mikkola

Carey Ma

Jon Parr

James Rakocy

Kobus Jooste

I'm going to move this list over to your podcast thread, so as not to totally hijack Louise's discussion...

R.K. Castillo said:

Thanks @Vlad  

Who do you think I should interview next?

[R.K. Castillo]

Sounds good....Jon Parr added a bunch of people as well

[Jason A.]

The reason I'm done is not because you guys don't agree with me, it's the pedestal you all have put yourselves on...I'm glad you guys know everything, I'm glad you guys are super popular in your inner circle. So popular that I must tread lightly....

I mean I have done it both ways but have you all? I'm not talking about pumping fish shii from another raft into the raft next to either.

No worries though and no hard feelings....

Good day/evening/night whatever it is in your time zone :-)

[Jon Parr]

Jason, I told you to "tread lightly" because you directly insulted Alex after he humbly relayed some valuable insight. It's my job to help Sylvia weed out the disrespectful D-bags on the forum.

You are entitled to your opinions, and to state them openly, and to defy others on the forum (as you did Alex, Ryan, and I by saying "Sorry but agitation of the water doesn't have anything to do with keeping the gunk off your roots. That is false...I'm telling you the information you are giving is wrong.") Dandy. Good for you. Make a bold statement and make a case. Teach us all a lesson. But don't be a dick by saying to Alex "Alex...I think you are lost or confused yourself. How did you become a moderator?", to which I simply replied, "tread lightly". That was a more tactful warning than I felt like giving. 

And then you whimper, waaaaa, the big boys are picking on me. I let you know you are in the minority with your idea, not to intimidate you, but to draw out a compelling argument. You make bold and contrary statements with no logical train of thought or evidence. Man up! I make no claim to be expert or elite. I do have great respect for the teachers and commercial aquaponics folks who have gone before me, and who have chosen to share their knowledge. You ask "Where did all these experts in aquaponics come from all of a sudden anyway, yet none of these experts are doing it on a LARGE scale, that I have seen anyway...if so please provide links. I am really interested. Also please don't send/post any links to these farms if they sell installation or consultation." Gee, let me think, Dr. Rakocy has taught aquaponics for over 30 years, on a LARGE scale, since before it was even called aquaponics, but he doesn't count because he also does consultation? So let me get this straight, you want links from LARGE scale experts, which means that they are both commercial and willing to share their knowledge, but not consult, because that makes them somehow un-qualified? I personally have only 5 yrs experience in AP, and I am building commercial aquaponics beds in a 350,000 sq. ft. greenhouse, but apparently I am not qualified as a LARGE scale voice because I also do consultations? Every LARGE scale AP person out there that is willing to share knowledge is also supplementing their income with consult, installations, and/or teaching. Are you LARGE scale? Do you teach, consult, or install? So only LARGE scale hobbyists that share but do not charge are qualified as experts? How do these aquaponics mystery farmers make a living?

I offered two personal experiences that directly counter your statement, and all you can do is ignore one, and say the other is "not very good". I disagree. I think they were both very good, and appropriate. You state that agitation does nothing to combat gunk, and that filtering and DO is everything. In my side-by-side black bass experiment, there is no filtration, no air pump or diffusers, hi DO on both sides, and a gunk difference like night and day between the two. "You do realize in your example that one of your rafts was pretty much a settling tank right?" Yes, I do, and that's precisely the point. Agitation (by fish movement) alone caused one side to be free of gunk, and the other to accumulate. "Yeah the stones and bass in the one side kept stuff stirred up and it was pumped into the other side with no where to go so it just stayed in there." Wait a minute...are you acknowledging that the bass motion (=agitation) did in fact keep it stirred up and moving, rather than gunking up on the roots of the bass side? Hmmm. "Still don't understand how you can say aeration helps keep your roots clean when the airstones themselves get dirty." I didn't say that, genuis, you did. That is your whole argument! There is great DO in an airstone, and the perfect environment for growing aerobic bacteria, which equals gunk! I said that agitation helps keep roots clean, of which there is very little on the surface of an airstone. Agitation from airstones is caused by the ascending air bubbles, and the very fact that airstones rapidly get covered in gunk is the torpedo in your DO argument. 

The point here is that, of course aeration and filtration are good for the health of plant roots, and of course modest agitation is too, whether it is from flow, ascending bubbles, fish movement, or whatever. My point, specifically, is that roots have less demand for O2 than fish, and under normal conditions a DWC with gunky roots may not be short of aeration or filtration at all, but simply not enough agitation. Good, healthy, beneficial bacteria contribute to root gunk, and detract from plant growth if allowed to accumulate in excess. Do and filtration do not prevent gunk, agitation does. Worm casting tea done right is absolutely thick with aerobic microbes, and the gunk is enough to plug 1/2" PVC lines, and it is dark chocolate brown. If it's not, add some molasses, more air, and keep brewing until it is. Compare the samples under a microscope, and you will see.

For a case study, start with clean AP water and add hydro nutrients. Keep DO hi in the res, and circulate at a rate that keeps agitation to a minimum yet hi DO to the DWC. Root gunk will be thicker than Beyonce's thighs.

I enjoy this process, by the way. Sometimes I change my views, sometimes I reinforce them, but either way I enjoy the process. Don't quit, and for god's sake, don't make personal attacks, whimper about being picked on, and then close with "No worries though and no hard feelings...." 

[Vlad Jovanovic]

Wow, I totally missed the whole..."Alex...I think you are lost or confused yourself. How did you become a moderator?" comment (skim reading, sorry)...that is a pretty asshole thing to say Jason, considering...

If you want to lay forth an argument to support a premise or idea...that's great...and usually very appreciated by all (particularly by the 'Secret Chiefs of the Inner Circle'...mwuhaahaahaahaaaa....who happen to enjoy learning new things just as much as the greenest newb does...maybe even more so...)...but saying shit like that is...well, let's just say that at best it's a pretty weak way to support an argument...at worst, it kinda does make you appear to be a douchebag (which you may, or may not actually be IDK)...

[Tim Day]

Let's all be happy aquapons!

My only experience with seeing airstones in raft systems was seeing the Colorado Aquaponics system at GrowHaus in Denver. There was one airstone that was offline, and the plants above it were definitely not growing as strongly compared to those which were directly above active airstones.

Not sure exactly if that was because of added oxygen or agitation (I imagine both would be beneficial) but the fact is, airstones under rafts only seem to help growth!

I suspect that the bacteria that live on the underside of the rafts, which require oxygen to do their thing, also greatly appreciate some bubbles