Backyard Aquaponics
A place to discuss aquaponics

Is it possible to grow lettuce with water continually flowing through the system?

Continuous flow, (no flood and drain) everything grows in it - just slower than flood and drain, and less filtration capacity.

does it slow down grow times significantly?

No.

The lower level of filtration is more an issue if you wanted to push the fish side a bit.

The lettuce and silverbeet in that system is nearly the same size as in the flood and drain system. I just hate how inneficient the continuous flow is

+ 1 but it has its place i just dont know where

Lettuce is generally quite forgiving of being water logged (compared to many other types of plants that is) if you are talking a continually flooded set up. Continually flooded will have more trouble with inefficient bio-filter due to lack of 02 in the water. A trickle feed (more like continually drained) is less likely to cause water logging of plants but doesn't provide much wet surface area for your bio-filter, also drippers or holes clog.

So to answer "Can lettuce grow in a continual flow system?" Yes it can. Lettuce is a pretty forgiving low demand crop in Hydroponics. If you can manage to get a little bit of mineralization (bio-filtration) going on in your system, lettuce will probably grow. As to other crops, results will vary.

If you are looking to do something kinda ornamental and just want to grow lettuce and a small number of fish, continual flow might be just the ticket.

On the other hand, if you want to support lots of fish, I will try to steer you to flood and drain.
Trying to get efficient bio-filtration with gravel, without flood and drain is often more trouble than it is worth IMO.

I'll echo your thoughts TCL....

I'm running (essentially continuously), "trickle" towers/troughs at the moment... mainly because I needed to acheive some oxygenation return back to the fish tank, and to cool the water as it was running through the solar array... and because I didn't have growbeds in place at the time...

Observations from my experience... cycling using continual flow and/or trickle towers will take much longer than using flood and drain.... with the nitrite "spike" being extended considerably... and likely to return almost immediately if you "stir" up the media at all...

i.e ...if you pull plants out.... or if you over feed... so you need to be aware of that if you're stocked with fish...

Over the next week... I'll be converting everything (and adding new beds) to flood and drain... with siphons or standpipes....

IMO... you just can't beat the reliability, ease of management... and the results....

thanks for the help,but i should have explained the system first.
1000L pond with a overflow pipe running into a "header tank".from there the water runs into four 6m gutters with clean stone chips,the water is drained via a overlow pipe and four loop siphons.the water is then fed into three 3m gutters of duckweed(free food),this runs into a large sump and is pumped back into the pond via a biological filter.will this system work is the big question

Can't see why not... with the loop siphons... it's more a "flood & drain" system with continuous pumping (flow)....

Essentially the same as many other member systems... only you're using gutters instead of growbeds...

I'm intriqued though... how deep are the gutters... and how do you get them to siphon... thinking of small height hydro style gutters...

How a bout some pictures... would make it easy to understand the setup...

One concern would be the possibility of the gutters/stone chips becoming blocked over time by solids.... most of us "pre-filter" the water before running through gutters...

OBO has had some experience with using media filled half pipes, kinda like what some might call small gutters. I believe he ran into some trouble with roots blocking the flow.

If the troughs or gutters are big (more like long grow beds,) then I expect you will be fine growing most types of smaller plants. If you are talking shallow 4-6 inch wide gutters, then be prepared to deal with both solids causing issues and roots blocking the free flow. It may still work, you just need to be prepared and keep an eye on those two things over time.

I've grown things hydroponically in media filled troughs that were only about 5 inches by 5 inches and 6 feet long. It did work but as roots built up, I needed to watch out for overflows when roots blocked things up.

In South Africa we have to basically improvise with everything, so I’m using roofing gutters. They are in a D shape 8cm deep by 12.5cm wide. This project is a collaboration between myself and the municipality of the city I live in. Like many countries on our continent we’re running out of food at a rapid pace, myself and the team we’ve put together are trying to do a little to change this, but due to some very stubborn “old school” thinkers funding is a little scarce so it’s mostly funded by our team. Change the world one step at a time and I believe this is the way forward. I’ve been looking at this site for some time and I knew that I would get the advice I need-thanks guys

the University of the Virgin Islands is doing nothing else but growing vegetables on a continuous flow system, Sa Aqua
they are one of the pioneers of AP
see:
http://www.uvi.edu/pub-relations/uvi/home.html

frank

If you use 90mm PVC and sit it in 100mm PVC then if it starts to overflow you can tell without filling up your backyard and emptying your tank. Just T off the 100mm so you can tell when the water starts to flow.

I wouldnt use gutters that size.

You need a lot more depth / width, at least 200mm. Smaller will work for a couple of months, but then everything will get blocked with roots and crap. It is a major PITA.

My first system was constant flow 'gutters' 75mm deep.

+1 ... I think in gutters that size, that you will need to pre-filter the solids... that flood & drain with loop siphons just isn't worth the effort...

Think you'd be better just running them ala NFT.... or investigating floating raft/fast flow ala UVI...

IMO... you need to have gutter/channels at least as big as those that Synaptoman is using in order to do "flood & drain".... with or without solids removal...