Aquaculture Overview

Aquaculture is the controlled cultivation of aquatic organisms, including fish, molluscs, crustaceans, and aquatic plants. Globally, this helps with food security, relieving pressure on wild fish stocks while providing a predictable source of nutrition. Locally within the Maldives, establishing sustainable aquaculture frameworks reduces dependence on imported produce, and helps to preserve marine ecosystems.

The primary objective of our project at Landaa Giraavaru is to develop an Integrated Multi-Trophic Aquaculture (IMTA) system. By intercepting the nutrient-rich water outflow from grouper grow-out tanks, we can repurpose dissolved nitrogen and phosphorus to fuel the growth of high-value seaweed. This method lowers environmental waste while producing quality sustainable ingredients directly for the Resort’s culinary teams. The land-based setup allows us to control environmental variables (sunlight, water flow, herbivorous predators) to improve production techniques, and encourage deep pigmentation in the macroalgae species.

Sea Grapes (Caulerpa racemosa)

Sea Grapes were selected as our primary focus. Sourced originally from the local island of Kihaadhoo, initial samples were transferred to an expanded sea pond receiving direct, nutrient-dense outflow of fish waste water from the grouper tanks. Early cultivation faced immediate micro-environmental hurdles, as shallow depths coupled with excess sunlight caused some tissue degradation. As a bonus, we routinely harvest any herbivorous predators (mainly sea slugs and sea snails) to use as food for the residents in our Fish Lab.

After several months, operations scaled up with some infrastructure upgrades, including reinforced concrete walls and improved filtration. Some sea grape areas are mainly focused on water filtration and nutrient uptake, while others are specifically managed for biomass production for kitchen consumption. A simple cultivation technique using small vegetable crates stocked with sea grapes proved effective by optimising water circulation, simplifying harvesting, and isolating the algae from grazers. We initially trialled shade cloths to block sunlight, but have now increased the depth of the cultivation area, providing better protection from direct sunlight, reducing stress on the algae, and resulting in longer algal fronds with more vibrant green pigmentation.

Early months produced modest monthly harvests of 225g-750g, but by mid-2026, our optimised 25-tray layout was delivering more than 4kg of sea grapes to the resort’s kitchens each month. This comprises of daily deliveries of 50g to the Main Kitchen and 100g to Blu Restaurant. We also provide an additional 200g for the Seafood Night special at Blue, with extra quantities on hand depending on kitchen requirements.

By June 2026, with the completion of the new ‘Marine Landaa Garden’, we had recorded an impressive 35kg increase in biomass. The garden functions as a small integrated ecosystem rather than simply as cultivation area. Different filter-feeding and detritivorous organisms contribute to nutrient cycling and are relevant to improving the overall water quality of the system.

In August, we carried out a restructuring of the sea grape culture garden to maintain optimal growing conditions. Regular deliveries to the resort kitchens continued, totalling 5.6kg of sea grapes by month-end. Biomass management will continually be adjusted according to kitchen demand, ensuring a balance between sustainable production and operational needs.

Elkhorn Sea Moss (Kappaphycus alvarezii)

Introduced as a promising candidate due to its high levels of carrageenan (a usable natural gelling agent) initial 5kg stock of Elkhorn Sea Moss faced immediate biological pressure. An early attempt to cultivate the red macroalgae on 20m longlines secured by metal rods in the open lagoon failed within days due to intense grazing by wild herbivorous fish. We relocated the remaining biomass to a controlled tank environment, suspending 1m rope sections inside 1000L tanks, supplied with circulating grouper effluent. Growth was slow during the first month, but the cultivated algae remained healthy and resisted decay.

To resolve ongoing issues with persistent filamentous epiphytes, the remaining biomass was transferred directly into the sea pond, where it demonstrated steady growth. After several weeks, the stock expanded from 150g to 340g wet weight. We systematically categorised the culture into distinct green, light-brown, and red-brown morphotypes. Separating distinct colour strains allows us to supply the kitchens with variations in texture and pigment to explore different recipe ideas.

While the newly introduced light-brown morphotype grew very quickly, it proved susceptible to epiphyte colonisation and localised herbivory. Subsequently, a new 3kg culture was installed next to the marine grouper cages in our large turtle rehabilitation enclosure out in Landaa’s lagoon. This layout provides good water flow, stabilising the total standing biomass at 3.6kg.

Blue-Green Spirulina Algae (Arthrospira platensis)

As part of the ongoing expansion of our microalgae system, in March 2026 we introduced a new species of Spirulina into the Fish Lab to evaluate its potential applications and establish reliable in-house biomass production.

We started with a ‘Spirulina Grow Co’ kit to provide a simple, controlled environment during early growth. To transition from an experimental phase to stable long-term production, extensive trials were conducted to refine key environmental variables:
– Light Intensity and Salinity: Tested in various combinations to identify optimal conditions for consistent growth.
– Nutrient Profiles and Mineral Salts: Evaluated across multiple trials to determine the most suitable mineral salt sources for sustained performance.

After developing this new protocol, our focus shifted to increasing the biomass. Initial expansion scaled up from a 1L culture to 5L of actively growing biomass during May, and soon expanded to 20L containers from July. We are now exploring filtration and drying methods, to evaluate food-grade processing protocols for future harvesting to supply the Resort’s kitchens.

During August, we scaled up our production to evaluate and optimise the most suitable methods for maintaining continuous biomass production. The objective is to optimise conditions and increase production to 1g dry biomass per litre of culture. Our partial-harvesting removes a portion of the biomass while maintaining sufficient culture density for continued regrowth, allowing for a consistent and sustainable harvesting cycle. The use of different culture formats (bags, buckets, flasks) will continue to be evaluated in order to improve productivity, maintain stable cultures, and establish a reliable production system capable of meeting the monthly supply target.

The harvested Spirulina was collected, dehydrated, and stored in dry form in preparation for its delivery to the resort restaurant starting in September. The initial production target is to provide approximately 20g of dry Spirulina per week.

Brown Marbled Groupers (Epinephelus fuscoguttatus)

Introduction

Fish “grow-out” is the phase of aquaculture that sits between the hatchery and the harvest. Juvenile ‘fingerlings’ are moved into a tank or pool environment, for rearing under controlled conditions (nutrition, stocking density, water quality) until they reach adult ‘broodstock’ maturity.

Globally, demand for seafood keeps climbing, but wild fisheries are under mounting pressure from exploitation and habitat loss. Slow-growing reef groupers are a popular food source across the Indo-Pacific region, so grow-out programmes can be important conservation tools. In an island resort setting here in the Maldives, we can reduce dependence on locally caught and imported seafoods, by substituting fresh and fully traceable fish to hotel kitchens, easing pressure on wild grouper populations. This also allows us to expand our hands-on skills through research and the refinement of new farming systems.

Our project aims to create an operational grow-out operation for the brown-marbled grouper (Epinephelus fuscoguttatus), built from captive-bred fingerlings supplied by a government hatchery. The goal is to rear fish for the Resort’s kitchens, and to generate the skills and procedures to refine our grouper husbandry techniques.

The brown-marbled grouper is a carnivorous predator; the juveniles are territorial and hierarchical, and require grading by size to minimise conflict and possible cannibalism. Grouper growth and immune function are linked to diet quality (particularly lipid and micronutrient content) and the species is sensitive to dissolved oxygen levels, water exchange rate, and handling stress.

Project Origins

The programme started in November 2023 with a single batch 75 fingerlings averaging 21cm/220g, supplied by the MMRI government hatchery (Maldives Marine Research Institute, South Malé Atoll).

Our land-based infrastructure has grown considerably, expanding to nine active 1000L flow-through tanks that enable us grade the fish by size. Over time, essential improvements have included lateral shading (which cuts heat load and reduces algal growth), and daily bottom-siphoning of uneaten feed and waste (keeping ammonia and nitrite levels near zero).

Our sea-based facility started in January 2026, with a pen constructed inside the turtle rehabilitation enclosure to take advantage of the natural water exchange and oxygenation that land-based setups cannot match.

Stocking, Grading, Management

Successive grouper deliveries have scaled up operation, with around 200-300 new individuals arriving in 3 separate shipments during 2024-2025, maxing out the land-based tanks with over 500 fish. Original sizes have ranged from 8cm/62g up to 21cm/220g juveniles, followed by the important size-grading step.

We have found that growth suppression and possible mortality can rise if population density exceeds 80 groupers per 1000L tank, so we have settled on 50–70 fish per 1000L for juveniles. The monthly size-grading tasks are scheduled to divide individuals by weight across separate tanks. Due to differences in initial size and subsequent growth rates, we have even merged stock from the different batches for regrading. This has proven effective at flattening dominance hierarchies, reducing ‘bullying’, and equalising feed access. We can now expect 50g of weight gain per fish over approximately 80 days, enabling us to forecast harvest time and feed allocation.

Feeding Strategy and Nutrition

Refining the optimal diet has been challenging. Initially, we used tuna trimmings from the kitchens, later supplemented with commercial dry floating pellets, but the fingerlings tended to ignore the surface feed. Our breakthrough was to use finely minced baitfish (mainly fusiliers), with seasonal anchovies and silver sprats (rehi in Dhivehi) – importantly, this includes the skin and whole internal organs rather than just trimmed flesh. This single inexpensive and locally sustainable change was found to reduce skin conditions.

Thanks to increased experience, food rationing has become more data-driven. Feed is now weighed before and after each session to calculate actual consumption. Individual daily intake rose from 1.5g/day in newly-arrived four-month-old fingerlings, to 1.9g/day within a month. As the fish mature, we have seen feed increase from 3.6g to 4.9g/day, with the older individuals consuming anywhere from 145g to 250g/day. At the facility scale, total monthly feed has stabilised in the 25–28kg range. Feeding frequency is tailored by size class: smaller fingerlings are fed twice per day to support rapid early growth, while larger juveniles and adults are fed daily or on alternate days, specifically to guard against overfeeding and  possible swim-bladder complications. One observed dip in consumption was traced to feed quality rather than loss of appetite (we resolved this by vacuum-packing silver sprats to preserve nutrient content).

Health Management

Two separate failures in water flow contributed to most of the mortalities recorded to date. In February 2025, an overnight circulation fault resulted in the loss of a batch of 25 groupers, while a second flow failure in May wiped out most of another batch. Lessons were learnt, so protocols now include daily pump and flow verification checks, essential even in a mature aquaculture system. Apart from circulation, the second most important procedural improvement is to regularly size-grade our fish and monitor stock-density.

We have seen and managed minor skin conditions and some instances of swim-bladder dysfunction (individuals swim inverted, typically linked to overfeeding or dietary imbalance). Cases were managed through prompt quarantine, withholding feed, and close observation, consistently allowing affected individuals to recover and rejoin the main stock. Apart from the early losses from water flow failures, mortality across hundreds of individuals raised in our land and ocean-based populations has recently fallen to small numbers.

Sea Pen Integration

In the lagoon at Landaa, we have a large circular enclosure used for final-stage rehabilitation of rescued sea turtle patients; within this, we constructed a separate pen to raise our groupers. This sea pen was stocked initially with juveniles from Maniyafushi, although transport stress caused some mortality. We have now started periods of quarantine and salinity/temperature acclimatisation, and since then, results have been excellent. By March 2026, the pen held 203 individuals in good health, being fed 1.5–2.0kg of baitfish daily split across two sessions, chopped into 1cm cubes to prevent choking and reduce loss to lagoon currents. During some stormy weather, we experienced damage to the netting and saw several escapes, so we have now completely rebuilt the pen structure with heavy-duty mesh, reinforced panel joints and double-anchored moorings.

Our sea pen trial has been a success due to the benefits of superior water exchange and natural oxygenation that land tanks cannot replicate. As the fish have rapidly reached average weights of ~650g by mid-2026, the first pen-raised groupers are already reaching the resort kitchens.

From Tank to Table

In March 2025, some 16 months on from inception, the first ten groupers (averaging 1.25kg, 37cm) were served during a guest-chef culinary event at Blu Restaurant. Further harvests followed through 2025 as more fish reached target weight, and by March 2026 we had established a sustainable supply of 15 individuals per month to the Resort kitchens, with capacity to deliver up to 30 groupers for special events.

By mid-2026, the standing stock across land tanks and sea pen is graded into clear size tiers (sea pen: ~650g, land: 300g/500g/750g). Going forward, we are able to forecast the harvestable biomass over the upcoming months. Trajectories start from fingerlings (60–120g) that grow reliably to 600g-1.2kg within 12-18 months under our current protocols.

Lessons Learned and Going Forward

What began in late 2023 with a small batch of 75 fingerlings in a handful of tanks has become an integrated grow-out system producing kitchen-ready groupers to a predictable monthly schedule. Through hands-on experience, our project evolved into a successful fish farm that starts with quarantining, and progresses through grading and feeding protocols in both land and sea-based systems.

Going forward, redundant pumps and flow-monitoring alarms will be a useful addition to our infrastructure. Closely recording food consumption against fish growth per tank enables us to optimise production using minimal feed. Regular inspections of our sea pen infrastructure are now followed by prompt repairs when necessary.

EDUCATION AND OUTREACH

During August 2026, we participated in two scientific conferences and presented our project “From Fingerlings to Plate: An Integrated Multi-Trophic Approach to Grouper Aquaculture.”  To a wide audience of local and international marine scientists, we shared our ongoing work to develop sustainable grouper aquaculture with the integration of complementary biological systems.