Farm Design

The cultivation method and farm design (which are highly influenced by the individual site conditions), will determine what type of equipment is needed on the seaweed farm. For the grow out at sea, there would generally be some type of anchor, ropes, culture lines and floaters be required. In most cases a boat will be required by the farmer.

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The depth of the water at the farm site is the main indicator what cultivation techniques and therefore farm design will be used for growing the seaweed

In shallow areas (0.3 – 2 meter depths during the lowest lowest tide) the fixed off-bottom method is very common, where wooden or steel stakes are holding lines in place that are suspended below the surface.
In deeper waters, the hanging long-line, floating rack and multiple raft long-line methods will be used. In these countries, seaweed is mainly growing in areas where the sea has a maximum depth of 15 meters.

Fixed-off bottom cultivation

Hanging long-line cultivation

Floating raft cultivation

Illustrations adapted from University Malaya

Going further offshore is not only more expensive, since more material and boat fuel is used, but also exposes the farm to higher risks, due to typically increasing wave height. There are at least a handful of other cultivation techniques and many unique design variations to set up the farm. In the fixed- off bottom and floating rack method the line length usually does not go beyond 10 meters. However in the floating/ hanging long line method the length of each culture line can be much longer and vary quite a bit, depending on the farm location. Less exposed areas can have longer lines, however also the handling of a longer line can be a limitation.

Farm designs highly depend on the location characteristics

Different anchors

In terms of anchors, wooden stakes are commonly used across all regions. They are set up with pure manpower. In overhead high waters, this requires skilled free divers in the community. 

!Good to know! Wooden stake anchors are in some regions preferably made out of mangrove wood because of their durability in the water. However, by law, mangroves in the Philippines and Indonesia are protected.

Rope material

The culture lines are somewhere between 4 and 7 mm in diameter. In floating long line systems, the lines connected to the anchor (rig lines) are usually stronger (10-14 mm) – the strength of all ropes used depends both on the farm design and exposure of the site.

The lines are a substantial cost in setting up a farm and in most cases common polyethylene ropes (PER) sold in local variety stores or provided to the farmers by the local dealers. The prices for a roll of 200m rope are somewhere between 10 and 15 USD. Under normal conditions, these ropes can last up to 5-8 years. Frequent cleaning of the culture line after each cycle will help to keep them intact and also reduce the contamination of disease, epiphytes or similar.


As floaters, used PET (polyethylene terephthalate) bottles are most commonly used to keep the culture lines floating. In some regions, only one type would be preferred, elsewhere all sorts of bottles are used. Farmers reported large differences in how long these bottles last them. Depending on the type of PET bottle, they would have to be replaced every  2-3 cycles. Although there have been some initiatives to introduce manufactured floaters (rubber floats) from more durable materials, after all the farmers prefer the bottles since they are very cheap and practical. They noticed that the surface of the new introduced floaters allows more biowaste to attach and the additional weight lets them sink faster. The PET bottles on the other hand have a cleaner surface, where this process happens much slower.

Explore another seaweed species:
Eucheumatoids  |  Saccharina |  Undaria  |  PyropiaGracilaria

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