Murrays Floating Raft DWC system

[Murray]

I have been trialing several variations to the "Floating raft" concept for some months. Our variations have been around finding a simple but very effective filter system to remove those very fine solids that are in an aquaponics system.
We wanted to make a system that could be used in a home situation but could also double as a pilot system for someone who has a mind to go into a small scale commercial system at a later date.

Obviously we already have our commercial system equipment that has gone into one farm at Mildura and several other individuals have used our very fine commercial tank and particulate filters. But , obviously this equipment is too big for a domestic application.

I have felt for a long time the need for a small scale domestic "floating raft" system

For this new domestic scale system the design difficulty is for a very effective but simple filter system. We have no difficulty in making any new piece of fiber glass equipment we need, but finding a filter system has caused us to experiment with some not so successful and moderately successful configurations and filter materials.

It had to be able to remove the very fine solids
Easy to clean and maintain,
and above all else, it has to be shown to work.

During all these filter trials I have had a poor lonely fish in there enduring the frequent water pump outs and re fills, while we fit a new outlet or whatever.

Just last week we filed the grow bed above with clay pebbles (again) and planted some greens in it.
The grow bed above is the primary solids filter (and bio filter) and the secondary fines filter and distribution box is situated below.

The system runs on the CHOP system, keeping it to one pump and constant height in the fish tank.

The areation system is fitted and works a treat, although I feel another modification to that coming on...:)

Now that we reckon we have the system design just about right, we are about to plant out the first lot of lettuce this week for the grow out trials.
It will not be until then that we finally see just how good the filter system really is.

[Jason Palenske]

What type of material do you plan to use for the raft?

[Dufflight]

Going to set up a floating raft system later and was looking at mussels for water polishing after the filter for solids.

[Murray]

Hi Jason,
It is a medium density polystyrene board 25mm (1") thick.

[Jason Palenske]

Hi Jason,
It is a medium density polystyrene board 25mm (1") thick.

Now will you be using one solid piece or multiple pieces? The reason I ask as some hydroponic farms use sectioned pieces so that they can assembly line older plants through such as lettuce in a constant manner.

[aussieap]

I really like the idea of floating raft for the home Muzz.
It means we can use the solids in other garden beds around home as a bit of a soil tonic. Also gets rid of those anaerobic zones in media based systems that must develop over time.
It also gives FAR more temperature stability to the system water which is much better for the fish.
Does your secondary filtration allow time for mineralization of those fine solids like Dr Rakocy was talking about?

Look forward to seeing how it travels through the trials.

[GaryD]

Hi,

I've believed, for a long time, that raft systems are under-represented at the backyard level.

Given that the very successful UVI model has been around for over 20 years......and is so easy to scale down.....it is interesting that it has taken so long for backyard raft systems to emerge.

The likely explanation is that media-based system were successfully popularised from the outset in Australia......to the point where raft systems remained in the background.

Another explanation is that media-based systems are deceptively simple to build and operate......and they produce reasonable results for modest effort. By contrast, raft systems are a bit more complicated and they require a higher standard of management.....particularly when it comes to the removal of suspended solids.

In addition to the greater temperature stability, raft systems allow for higher stocking density......and a higher feeding rate (which translates into faster fish growth).....than a media-based system fish tank of the same size. Alternatively, the system can be run at the same stocking density but with much lower risk. Either way, it's a compelling benefit.

I'm looking forward to seeing how the new system performs. It will certainly stimulate some interest and, will hopefully spawn many new raft installations.

Good luck Murray.

Gary

[Dufflight]

Great concept to incorporate into exsisting systems as well. A lot of the media filled gb's are allready filtering the water so can still be used as the bio filter and pre filter for solids. Just have to find an effective suspended particle filter and water polisher to but in between the gb and DWC beds.

[nwestwood]

I gues I have rushed into this one. My system has both grow beds and floating raft, but it's just barely set up and the first lettuce seeds are sprouting. I assume the problem is that the fine solids will settle out to the bottom of the tank or get entangled in the root masses. Then what? I'm going to be finding out it seems. Maybe putting a chunk of something under the water inlet to catch the particles, and clean it periodically? Or pump water from the sump tank to the DWC, so it has passed through the grow beds first? What are everyones thoughts?

[Laurie]

I have attatched some pics of a small raft system I have. They come as seperate pieces and attached with clips. All plastic.
Laurie.

[Murray]

HI nwestwood,
The suspended solids will attach themselves to the roots and initially promote good growth, but as the plant grows the solids will continue to adhere to those roots and eventually stifle the oxygen supply to the plant roots causing poor growth and in some cases even the death of the plant.

That is a nice system Laurie, I have seen one of those systems recently somewhere. Very neat.
I finally got around to ordering those cucumber seeds you recommended several months ago. Now I can't wait for them to turn up.

[Murray]

Yesterday afternoon we planted up one of the floating raft beds with Lettuce and basil,
20 lettuce and 29 basil to be precise.

In the grow trough layout there should be 50 growing holes, but we loose one for the water inlet from the filter box.

The lettuce are showing hair like root growth already (14 hours later, overnight) down into the water column. Unfortunately my "happy snap" digital camera. is not good enough to take close ups of that type.
I obtained the seedlings from a nursery shop, mine are not yet ready to plant out.
I washed the dirt off half of them and left it on the other half just to see if there is any difference in performance or early recovery from transplant shock. I have got to say that there appears to be no difference at this early stage.
The basil plants also came from the nursery shop and I washed all of them clean before placing them into the net pots. They all look fine this morning.

http://aquaponics.net.au/blog/wp-content/uploads/2009/03/frsystem4-400x300.jpg

http://aquaponics.net.au/blog/wp-content/uploads/2009/03/frsystem5-400x300.jpg

[Castaway]

Looks Terrific Murray. Very professional. Look forward to seeing how it performs over the coming weeks. You might need to do some animation of this system like you did for the CHOPs system. :)

[Tomer]

Hi murray
looks great.what is the black plastic oval tubing inside the raft tank? is that for aeration?
for the seconds filter, is that a tight mesh screen or rather something denser?

[Murray]

Hi Tomer,
The black 19mm tubing is for aeration but proved to be unsatisfactory. It, the black tube, floated to the top and also the holes allowed the use of to much air from the compressor.
We now have the same black tubing attached at each end but with two rows of small air stones inserted, 14 in all to deliver air more evenly. This arrangement consumes much less air from the compressor.
All parts of the trough get air, especially once the foam sheet is on top. The air bubbles tend to be dispersed by the flat foam sheet to all areas at the water surface, even the corners of the grow trough, which is very good I feel.

The fines filters are plastic trays with a couple of different grades of filter material.
The material is easily washed out and collects the fine material very well.
Just how well will be seen in the next 30 days as we can observe the plants to see how much fine material adheres to the roots.

We have tried several different filter materials to date, some were not good enough, some were a bit too good and blocked too quickly.

The primary filter is a trusty regular 300mm deep grow bed with clay pebbles as the media. The water auto siphons out of there and is split into two streams to go through the two filter trays below. The water flow is then split to each grow trough.

The filter box that holds the filter trays and disperses the water had to be strong enough to hold the weight of the grow bed above estimated to be around 175 kg. The only material good enough for that task is fiber glass.
This arrangement allows us to keep to the CHOP principle of constant height in the fish tank and grow trough and only one pump to run the system.

The design criteria was

Keep to the CHOP principle,
Ease of maintenance for the householder,
Filter material must be replaceable and inexpensive,
The system must be compact,
The system must be expandable,
The system must be transportable.

[Tomer]

looks really nice, murray, seems you achieved all the goals. so how often will the filter need be replaced and/or cleaned? and just how fine the filtration has to be? i assume the size of the throughs allow you to have quite high fish density. i guess with the compressor, aeration won't be an issue..
is the ratio of FT:GB same in a raft setup, or is it much larger through volume to FT volume?
and what are your conclusions regarding washing the earth off the roots before setting the plants in the throughs?

[Murray]

Hi Tomer, re washing the earth off. Don't know the answer to that. I have planted some each way. There appears to be little difference in the performance so far. In the end I feel appearance would be better , from a marketing point of view to plant them without the dirt. Cleaner root mass at the end I imagine.
The EC of the system is a steady 1, so there is plenty of nutrient.

I am trialing a different method of cycling a system. Using CANNNA bio Vega at 1/4 strength and it has turned out to yield am EC of exactly 1, which is good.
The product had a good quantity of nitrogen in it which is giving a mid range ammonia reading immediately. And it is a safe nitrogen, unlike urea.
I am testing every day and will be glad to see the nitrite kick in and so on.

The first two days I cleaned them daily, but since then I have not cleaned them. The real test will come when there is a fish load.

I will load the system with 50 Jade Perch from a batch of 150 I have that are 6 months old, so there will be an immediate fish load.
I will not do that until there are good signs of the system cycling, very low or no ammonia in the system.

The water has gone very green with algae, I had the water exposed to the sun for several days before covering the troughs with the floating rafts.

Friday we made the Kiddie Cover door for the fish tank, so that will go on tomorrow.

GB to FT ratio in this system is one to one, but I am sure it could go much higher, 4 or 5 to one easily I reckon, especially if growing low feeders like lettuce and basil. When this first batch of plants has settled down I will hang another two troughs off the side somewhere to test the ratios.

[Tomer]

Hi murray
from what i read on there website, CANNA states that the BioVega is assisting the plant growth phase, releasing the Nitrogen Betaine according to the 'plant demand' - is it affective as a cycling agent then? won't a handfull of bird excrement (pardon my french) do the job better and less costly?
just curious..
they have good products. will be happy to hear about your experience with the BioVega.

[Murray]

Hi Tomer, you are possibly correct re the bird droppings, but not everyone can easily get sufficient bird droppings, whereas everyone can get some Bio Vega. It is not all that expensive anyway in the overall scheme of things.

I certainly provides a good shot of nitrogen immediately with no leaf burn to the seedlings.
I have found that 1/4 of the recommended mixing rate works fine giving an EC of 1 and ammonia reading of 1. The ammonia reading in the system has not dropped off at all, but it has only been a week.

I suspect that 1/8th strength would possibly have been enough. I will try that in the next new system.

There is some early signs of Nitrite but only just.

The hair like new root growth is great. I wish my camera would do close ups.

I have one sacrificial fish (Jade Parch) in the system that is doing just fine.

The water is still very green with algae.

[Dufflight]

If its a digital camera it may do macro. Its an option that is usually turned off in there menu. And only works on un-zoomed shots.
Did you start the system off with AP water to give it a faster start up.

[Murray]

Hi Duff, No I did not start with water or anything from one of my other systems, just tank water. I wanted to see just how long it takes using Bio Vega as a test and to see if it worries the lone fish at all.

Some root pix

http://aquaponics.net.au/blog/wp-content/uploads/2009/03/frsystem6-400x338.jpg

Above: This one had the soil washed off the roots.

http://aquaponics.net.au/blog/wp-content/uploads/2009/03/frsystem7-400x350.jpg

Above: This one was dropped into the net pot with the soil attached.

[Tomer]

Hi murray seems that leaving the soil on gives then a bit of a better edge.. perhaps just slightly. if the Biovega got you ammonia of 1 and an EC of 1 it's doing the job just fine.. here in Israel all of these bio products are expensive, unfortunately, everything good for the environment almost always costs more.. unbelievable, but this is how this country works still. so it's birdie droppings for me (though i read on some site that because of the danger of E. coli in animal waste, in order to be organic and safe the system has to cycle some 120 days before you add the veggies and fish.. that's too long on my agenda).
how long is the estimated growth period for the lettuce and basil in a raft system?

[Murray]

For lettuce it is 24 days from seed to plant out and 28 days from plant out to harvest.
Basil ? I will tell you in a few weeks time.
I note that the basil seedlings are much slower at taking off than the lettuce. They are putting down new roots, but not as vigorously as the lettuce.

I had a chef here yesterday looking over things, and he told me that the restaurant he works at has just switched from fresh basil and herbs to dried product. Part of cutting back on expenses.

Yesterday I dropped 20 Jade perch into the Floating Raft system to keep company with the one Jade Perch that has been the test victim to date.
Now we will have a fish waste load on the system. It will be interesting to see how the ammonia levels etc work out. I am a bit early in adding the fish, as the system has not cycled yet, but we will see how it goes.
The Jade perch are 7 months old and are possibly around 250 to 300 g each.

[Finn]

Hi Murray

What do you use to start your lettuce. Do you seed your AP system or do you have a separate setup for babies?

Finn

[Murray]

Hi Finn,

I have just gone back to raising my own seedlings again. When the sun comes up I will take some pix of my next batch of lettuce seedlings. (it is 4:45 am Wed here)

I have just purchased some new seeds of various kinds, cucumber, lettuce, cabbage, tomato, silver beet, broccoli.
Actually, because of the very organised way the floating rafts are set out I realise that there will be a glut of lettuce at my place very soon.

I just have to learn to be more frugal in planting out seedlings in a more organised way....say, only 2 or 3 lettuce a week. I don't know what it is about lettuce, but I seem to have that many I cant possibly use them or I have none at all.

This leads me back to this new floating raft system. If I were just going to produce lettuce, I am going to have difficulty in using up the nitrates produced by those 21 Jade Perch. I will really need to double or even triple the grow troughs....... say triple. I would then have 294 holes (grow holes) in the rafts and on a 28 day turn around, that would be 70 lettuce a week.
What a great system for a retirement village or rest home or school tuck shop. They could produce all their lettuce requirements in a very small, easy to manage space / system.