Culture of Gracilaria in Pond

Gracilaria is one seaweed genera which is used as raw material in producing Agar. There are other kinds of agar producing seaweeds but only Gracilaria, so far, is commercially farmed in the Philippines to name a few, G. firma; G. changii; G. heteroclada. Production/cultivation of in pond is highly adaptable and commendable, being a labor intensive project with cooperatively low capital investment.

Culture of Gracilaria

A. Site Selection

The success of farming Gracilaria is highly dependent on the selection of appropriate site since Gracilria species have different environmental preferences. Site to be selected must conform to the Gracilaria species to be farmed. Generally, for pond culture, a brackish water pond ranging from 1/4 ha. to 1 hectare with good water flow is manageable. The area to be selected should have the following parameters.

  • Water depth : 50 cm to 100 cm
  • Salinity : 25 to 28 ppt
  • Temperature : 25° to 30° C
  • pH: 6 to 8
  • Substratum: Clay loam; Sandy loam

B. Pond Preparation

Pond preparation will be done before stocking. The pond will be dried for several days until the soil cracks, then removing unwanted algae, shell and fish, and then will be treated through the application of agricultural lime at a rate of 500kg/ha. After a week water inlet will be introduced at a depth of 30-40 cm.

C. Seedling Preparation

Selection of seedling is one important factor for successful farming. Fresh, healthy with strong branch seedling must be chosen. Seedling stocked from the wild would give better production. However, healthy seedling from farm lines can also be used. The seedling from the nearest source is recommended to ensure easy transport to the site. The transport material such as styropore box is advisable especially in transporting seaweed to distant places.

E. Stocking

Stock Gracilaria early in the morning or late in the afternoon or during cooler part of the day by broadcasting method. The temperature and salinity from the source should not differ by 5° C and 5 ppt respectively with that of water in where Gracilaria will be stocked. The stocking density ranges from 5,000 to 6,000 kg/ha.

F. Maintenance

Management of the farm is very important. Unnecessary aquatic plants, epiphytes attached to seaweed should be removed manually to enhance the growth of seaweed. Frequent exchange of water will be maintained every week for the first month and bi-weekly exchange of water for the succeeding months.

D. Harvesting

Harvest seaweeds after 45-60 days of culture period. Select the young plants as seedling for the next cropping period. The harvested seaweed should be cleaned on site and transported to a drying area. Drying platforms with flooring made of bamboo, net, coconut palm or other form of flooring should at least be used in drying seaweed to get good quality products. Once dried seaweed should be packed in sacks, stored in a dry place and should be sold as soon as possible.

Cost and Return Analysis for 1 Hectare Farm


  • Species : Gracilaria spp.
  • Pond area : 10,000 sqm
  • Stocking rate : 500-600/sqm
  • Daily growth rate : 29 grams
  • Culture period : 45-60 days
  • Number of cropping/year : 5
  • Stocking method : Broadcasting
  • Pruning/cutting : Bi-weekly
  • Water change : weekly
  • Water depth : 50-100 cm

Capital Cost:

  • 4 pcs Rattan basket @150/pc – P600
  • 100 pcs Empty sacks @6/pc – 600
  • 2 balls soft tie @75/pc – 150
  • 50 m. B-net @20/m (optional) – 1,000
  • 2 roll P.E rope #8 @220/pc (optional) – 440
  • 1 pc Bolo @50 – 50
  • 5,000 kgs Agricultural lime @8.50/kg – 4,250
  • Total – P 12,090


  • Initial weight: 5,000 kgs
  • Final weight: 18,495 kgs
  • Biological loss: 10%
  • Gain weight: 16,645.5 kgs
  • Less seedling for next cropping: 5,000 kgs
  • Net weight for drying: 11,645.5 kgs
  • Wet to dry ratio (10:1): 1,164.55 kgs
  • Price per kilo: P9.00
  • Total sales per cycle: P10,480.95
  • Gross sales per year: P52,404.75


  • Transport cost (1.00/kg): P2.911.37
  • Total fixed cost: 12,090.00
  • Miscellaneous expenses: 500.00
  • Total expenses: 15,501.37
  • Net Income: P36,903.38

Note: Original article were sourced from SEAFDEC AQD, re-posted on this site with permission.

For question and more information, contact:

SEAFDEC Aquaculture Department
Tigbauan 5021, Iloilo, Philippines
Trunkline connecting all offices: (033) 336-2965, (033) 511-9170 to 71,
Email: [email protected]

Bureau of Fisheries and Aquatic Resources (BFAR)
National Seaweed Technology Development Center
Cabid-an, Sorsogon City
Email: [email protected]

Philippine Coconut Authority (PCA) Building,
Elliptical Road Diliman, Quezon City,
Tel No. : (02) 929-9597/8074
Email : [email protected]


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