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.