JurnalPost.com - Fish is a popular protein source in Indonesia due to its delicious taste and relatively affordable price. National fish consumption reached 26.08 kg/capita in 2025, an increase from 25.31 kg/capita in 2024.
Commonly consumed and farmed fish commodities in Indonesia include catfish, tilapia, milkfish, and gourami. According to data released by the Ministry of Marine Affairs and Fisheries of the Republic of Indonesia, 2025 production figures for these commodities included 1,679,393 tons of tilapia, 1,212,627 tons of catfish, 948,784 tons of milkfish, and 200,470 tons of gourami.
Challenges in Increasing Fish Farming Production
Efforts to increase fish farming production still face various challenges that can affect yields. These include declining water quality, disease outbreaks, and rising feed prices.
Poor water quality can increase the number of pathogens in the farming environment. This condition can also cause fish to become stressed, making them more susceptible to disease. Ultimately, fish growth can be stunted, potentially leading to mortality.
Therefore, the development of technology and farming systems is necessary to assist in water quality management while improving the fish's immune systems.
Understanding the Green Water System
The green water system is a fish farming method that involves cultivating microalgae, such as Spirulina sp. and Chlorella sp., in the water until it turns green before being used as a medium for fish rearing.
The microalgae grown in the water can be utilized as natural feed for fish larvae. Microalgae contain various nutrients required by larvae, such as proteins, fatty acids, vitamins, minerals, and various bioactive compounds. These components help improve fish growth and immune resistance.
In addition to their nutritional content, the size of the microalgae is also suitable for the mouth opening of fish larvae, making them relatively easy to consume.
Microalgae can also increase oxygen levels in the water through photosynthesis. Furthermore, they act as bioremediation agents by utilizing dissolved organic matter such as ammonia, nitrites, and phosphates. This capability helps maintain water quality in conditions that support fish growth.
Benefits of the Green Water System for Fish Farming
Numerous studies have shown that the implementation of the green water system has a positive impact on fish farming activities.
In catfish, the green water system is known to increase fertilization rates and egg hatching rates. Meanwhile, in tilapia, body weight, body length, and fry survival rates were found to be higher in groups raised using the green water system compared to control groups.
The use of the green water system with Spirulina sp. and/or Chlorella sp. for 24 days is also known to increase the survival rate and total length of gourami larvae.
The high survival rate of the fish is partly due to the system's ability to help maintain water quality. Better water conditions can inhibit pathogen growth while supporting the fish's respiration and metabolic processes.
In addition to catfish, tilapia, and gourami, the green water system can also be applied in milkfish farming.
How to Implement the Green Water System
In general, the implementation of the green water system can be carried out through the following stages:
Clean the pond using a disinfectant.
Add 8 g/m³ of urea fertilizer and 200 g/m³ of dolomite.
Fill the pond with 20 liters of water.
Add 1,000 mL of microalgae culture, or approximately 10–20 percent of the water volume.
Allow the microalgae to grow for approximately seven days.
After seven days, fish larvae can be stocked and reared in the pond.
In practice, the amount of water, microalgae culture, and other supporting materials should be adjusted to the capacity of the container and the type of fish being farmed.
Potential to Reduce Production Costs
The development of the green water system for rearing fish larvae is expected to increase farming production while providing economic benefits to farmers.
The presence of microalgae as natural feed has the potential to reduce dependence on commercial feed, especially during the larval phase. Consequently, a portion of production costs can be reduced.
Increased production can also be achieved because this system helps improve fish immunity and resilience while maintaining water quality. These conditions can ultimately reduce mortality rates during the rearing process.
Nevertheless, research and development of the green water system must continue, especially to determine the types of microalgae and optimal concentrations suitable for various types of farmed fish.
With proper development, the green water system has the potential to become an alternative farming technology that is more efficient, environmentally friendly, and capable of supporting increased fisheries productivity.
References
Amelia, R., Supendi, A., & MZ, N. (2024). Application of the Green Water System (GWS) on the hatching rate of Sangkuriang catfish (Clarias gariepinus) eggs. Manfish: Scientific Journal of Fisheries and Animal Husbandry, 2(2), 124–132. https://doi.org/10.62951/manfish.v2i2.58
KKP. (2026). Data and Statistics. https://portaldata.kkp.go.id/portals/data-statistik/layer1
Pratama, I., Susanto, Nopriyanto, R., & Nurhafid, M. (2024). Effectiveness of green water system as larval Gourami (Osphronemus gouramy) cultivation technology: Efforts to increase larval productivity. International Journal of Agriculture and Biosciences, 13(3), 469–473. https://doi.org/10.47278/journal.ijab/2024.146
Rizki, R. R., Kanya, M. R., Puteri, R. E., Prariska, D., Lestari, S., Guttifera, & Sari, S. R. (2025). Effectiveness test of aquaculture systems: Green water, biofloc, and aquaponic systems on the stress response of snakehead fish (Channa striata). Journal of Fish Health, 4(4), 273–281. https://doi.org/10.29303/jfh.v4i4.7838
Widiyanto, S., Sarto, M., Fitria, L., Yudo, R., & Suyono, E. A. (2018). Biochemical compounds and sub-chronic toxicity test of Chlorella sp. and Spirulina sp. isolated from Glagah Coastal Water. Journal of Biological Researches, 24(1).
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