Final report for FS22-339
Project Information
Culture of microalgae in commercial aquaculture hatcheries is therefore vital, costly, and has room to be optimized. We believe there are two areas commercial aquaculturists can improve microalgae nutrition and economics: (1) production of live spirulina as a live feed for zooplankton and (2) enhancing the fat content and nutritional fatty acid composition of diatoms through silca fertilization optimization.
Spirulina has been proven in literature to enhance the survival, growth, and immune system of marine fish and shrimp. It has extremely high protein content (60-70%) required by fast growing larvae, it lacks cellulose walls meaning it is highly digestible (up to 84%) compared to other algal species, contains a high amount amino acids such as phenolic acids, tocopherols, carotenes and linolenic acids and has been found to enhance disease resistance through chelating of toxic minerals such as arsneic and heavy metals containing several antiviral and antimicrobial propoerties. It is also relatively cost effective. Spirulina in powder form has been used extensively as a feed supplement in many aquaculture industries. However, live spirulina has not been as extensively utilized. Most likely because spriulina is not a commonly live cultured species in the industry, therefore many culturists are not familar with its husbandry conditions. At Live Advantage Bait LLC we experimented with culture of live spirulina and found compared to other microalgae species we culture, spirulina can be cultured at extremely high densities at a high pH meaning no additional use of carbon dioxide and at ambient temperatures of South Florida meaning no additional temperature control required. In addition we have found our isolate of spirulina can be used as a feed for zooplankton (rotifers) at our commercial fish hatchery, producing 2x the culture density of rotifers compared to use of standard practice algae paste products and without need for supplemental oxygen in the rotifer cultures. These preliminary obeservations demonstate live spirulina culture may enhance both economics and performance of marine aquaculture hatcheries.
However, literature also demonstrates spirulina must be matched with a high fat microalgae species, such as a diatom, to provide optimal nutrition to marine fish and shellfish larvae. Unlike culture of flaggelated microalgae, culture of diatoms requires additional fertilization of the culture environment with silica, as diatoms have silica shells. Literature indicates the nutritional content of diatoms can drastically vary with growth phase of the culture as well as silica availability. Limiting silica has been found to enhance nutrition content of the culture, however it can also reduce culture growth. Microalgae is often most nutritious during the exponential growth phase. Therefore a balance must be made between silicate limitation and growth phase. One way to enahance both production performance and nutrition is to utilize batch culture. Batch culture of algae starts with innoculating a culture vessel with a small amount of algae and sufficient nutrients to initiate rapid growth and then harvesting the entire vessel when the exponential growth curve, i.e. nutrition, is maximized. A culturists must therefore understand what the ideal amount of fertilization and silica to use on day 1 to innoculate the culture vessel and on what day the culture will be the most ideal to harvest. This will require understanding production performance as well as tracking nutritional content of the microalgae over time in order to develop a specific operating procedure (SOP) for the commercial aquaculturist.
In addition, the anticipated variance in nutrition of microalgae species over time and variable culture conditions is invaluable infomration to a farmer who has to make daily decisions on feeding rates and production to maximize margins. A project that describes anticipated microalgae nutrition as a factor of culture environment and time will be extremely valuable to a economically and environmentally sustainable industry.
This project will include three objectives (1) demonstration of live spirulina culture and use as a live feeds in marine fish and shellfish hatcheries; (2) development of a SOP for diatom culture to enhance production performance and nutrition; and (3) outreach/education
(1) Live Spirulina culture optimization as an aquaculture live feeds
Spirulina will be cultured at Live Advantage Bait LLC in 18inch diameter 4 foot high suntubes in 4-5 day batches. Production performance metrics will be recorded including cell density and size over time and temperature through three triplicate production runs at ambient temperature in South Florida summer, fall, winter, and spring conditions (daily production performance x 3, 5 day batches x 4 seasons). Mature spirulina cultures will also be utilized to culture rotifers in triplicate batches. Samples of the spriulina and rotifers, on day 2, 4, and 6 of culture will be sent to the New Jersey Feed Lab for proximate nutritional analysis (3 sample times x 2 sample types x triplicate samples = 18 samples). Spriulina will then be used as a live feed for Mercinaria mercinaria (hard clam) culture, greenwater in larval fish culture and the rotifers fed spriulina will be used as a live feed for Lagodon rhombiodes (pinfish, a marine baitfish) aquaculture in duplicate side-by-side experiments and production performance compared to standard commercial methods. Mercinaria culture will take place at Great Florida Shellfish, a commecial shellfish hatchery and collaborative partner on this project.
(2) Diatom culture optimization as an aquaculture live feed
Thalassiosira weissflogii (TW) is a large diatom (6-20µm x 8-15µm) that is used in the shrimp and shellfish larviculture industry. TW will be cultured at Live Advantage Bait LLC in 18 inch diameter 4 foot high suntubes. Known, and standard amounts of f/2 fertilizer medium and silica, will be used to culture 4 day batches of TW in triplicate, tracking cell density over time. The trial replicated reducing the amount of silica utilized by 20% each round until cell density, i.e. growth, is compromised. Samples of TW cutlures utilizing silica concentrations just above and at compromised growth (2 treatments) will be sent to the New Jersey Feed Lab for proximate nutrational analysis on day 2, 3, 4, and 5 of culture (2 treatments x 4 time periods = 8 samples). A SOP manual will then be developed on batch culture of TW for optimized nutritional performance.
(3) Outreach. Techniques for live spirulina culture and production performance metrics from Objective 1 and diatom SOP for Objective 2 will be developed into white papers and presented to industry through the Southern regional extension services as well as Aquacontacts and National Aquaculture Association (NAA) listserves and directly through minority groups within aquaculture. A webinar will also be organized to present these white papers, advertized through the same groups as mentioned prior. The papers will also be posted on the Live Advantage Bait LLC website for download. In addition, cultures of spirulina will be made available for 12 months post the completion of the project.
Cooperators
- (Researcher)
- - Technical Advisor (Researcher)
Research
Low Silica Diatom Culture
Two different species of diatoms (Thalassiosirra weissfolgii (TW) and Cyclotella nana (CN) ) were sourced from Eric Stenn of Algagen (farmer collabortor) and cultured for 7 crosses in disinfected (filtered to 1 micron, ozoned, bleached, and thiosulfate neutralized) natural seawater at Live Advantage Bait LLC and f/2 medium and silica per standard protocols. We determined 7 crosses was suitable enough to ensure cultures were acclimated to our facility water and culture conditions prior to experimentation.
Silica in the natural seawater was measured to determine a background baseline value utilizing a HACH spectrophotometer assay and reagents ( item #2107469 acid reagent high range silica powder pillows and item #2106269 citric acid powder pillows) per their standard methodology to measure silica from 1-100 mg/L. We determined our source water to be 3.1mg/L.
We then conducted culture trials in 220liter suntubes in duplicate for both standard culture proceedures for each species of diatoms (fertilizing 100ml f/2 and 150ml silicates sourced from Micro Algae Grow Mass Pack with Silicate from Florida AquaFarms standard media) and various limited additional silica added concentrations starting at 0 and increasing by 10% for each 4 day batch until it was determined the minimal amount of silica needed to be added to not significantly impeed growth compared to the control.
Brackish Spirulina Culture methodology
Spirulina cultures (Arthrospira platensis) were obtained from Erik Stenn of Algagen. For culture we utilized first 3L culture vessels of filtered, bleached, and ozoned water, scaling up to 18L carboys, then 220 liter suntubes for trials. We also experimented increasing the salinity from 8ppt to 30ppt over 5-10ppt increiments to determine the acclimation tolerance. When cultures reached a terbidity stick density of 5 or less, we harvested the culture utilizing a 15um mesh size, and started new cultures with 1/4 density. At first cultures were fertilized every other day with f/2 medium per standard literature protocols for freshwater spirulina cultures. And then we experimented with cheaper urea and tri-phosphate (T-super) fertilization. To feed urea and T-super, master cultures were made by dissolving 10g of urea in 1 liter freshwater and 2g of T-super in 1 liter freshwater. These master cultures were added to the Spriulina cultures at a rate of 10ml/L per feeding each.
A SOP was developed for holding, acclimation, and general culture. Cultures were monitored daily for density, appearance, pH and general behavior and culture conditions adjusted accordingly over several months utilizing trial and errors as to develop a standard operating procedure (SOP).
Braskish Spirulina suitability for hathcery utilization as a live feed and/or enrichment source
Spriulina at 30ppt and diatom cultures were scaled up to 200liter suntubes and utilized for several feeding experiments. First spirulina was utilized at a 30% incorpration rate in a live (Nannochloropsis sp.) algae fed rotifer culture. These rotifers were mainained in duplicate under standard ('control') live algae culture protocols and the 30% incorporation rate of Spirulina. Cultures were maintained for one week, and rotifer culture density, % gravid and amount of algae remaining in culture each morning before feeding noted.
After it was determined rotifers could be supplemented with Spirulina, a trial rearing pinfish (Lagodon rhomboides) commenced utilizing 300 liter tanks, stocked at 20 fertilized eggs per liter in duplicate for control, rotifers fed spriulina and spirulina utilized at 20% incorporation rate within the in tank greenwater. Larval survival and gut contents were examined after one week of culture.
A similar trial was also conducted for post set Merc. merc. hard clams at Tom McCrudden's hatchery. Clams were fed spirulina at a 20% incorporation rate and clam survival and gut contents noted after one week.
Low Silica Diatom Culture
We determined TW to grow well with 10% the normal silica addition and CN to grow well with 20%. On day 5, silica remaining in each culture was also tested. The silica limiting treatments had no detectable silica remaining while the control had 1.9-4.9 mg/L still in culture, meaning we found the true silica limitation point for each culture.
Next we cultured each diatom at the control and limiting silica amounts and took samples for nutritional analysis.
Nutritional analysis became much more difficult than origionally anticipated. The feed lab we proposed to analyze the samples determined our live cultures were far too dilute and liquid to be analyzed and they did not have the correct equipment to concentrate microalgae to a sufficient concentration for their laboratory. After contacting a few other laboratories, their cost for analysis was exponentially over our budget. Fortunately, colleagues at Florida Atlantic University offered to help, but we were limited to only one sample of one species of diatom. We chose CN, conducted the growth trials and they found: Crude fat: 0.168%; Crude fiber: 0.35% +/- 0.09%
As nutritional analysis is as important as understanding culture fertilization limitations, we applied and were successful awarded a grant starting July 2025 which will enable us to obtain some more nutritional analysis. We aim to publish a complete report with the full nutritional analysis by the end of 2025.
Brackish Spirulina Culture methodology
After several trails attempting to increase salinity of the culture from 8ppt to 30ppt, we learned several things about the culture: (1) It requires real sunlight and will not grow under artifical lights like other microalgae species; (2) it not only likes very hot temperatures, it also likes very high pH up to 10; (3) While most microalgae cultures grow in 4-5 day cycles, spirulina requires 10 days to complete the growth phase before harvest and re-innoculating new cultures; (4) the culture can be slow brought up to 30ppt but it will only last 2-3 growth cycles at this salinity before crashing. It is better to maintain a culture at 10ppt and only bring cultures to higher salinity as needed; and (5) While it grows very well with traditional f/2 medium, it can also be grown with urea and triphosphate.
We were unable to perform sufficent nutritional analysis on the cultures with the same issues as stated above for diatom nutritional analysis. However, we applied and were award a second grant from the Aquaculture Resource Council in the state of Florida to continue this research and obtain full nutritional analysis with Harbor Branch Oceanographic Institute.
With all these learned steps we developed a SOP draft document we shared with several farmers including Tom McCrudden to refine. We are still refining this document with photos and troubleshooting commentary and plan to publish by the end of the year with the additional nutrional analysis data from our new ARC grant referenced above.
Braskish Spirulina suitability for hathcery utilization as a live feed and/or enrichment source
It was determined rotifers could be grown and consume a live Spirulina supplemented diet, with growth rates and % gravid no signficantly different from controls over a period of 4-5 days of culture. During these first few days, it was found the Spirulina continued to grow and become more dense within the rotifer culture and we hypothesize the rotifers were consuming only the Spriulina that was degraded or broken down into smaller particles of sufficient size they could consume. On day 6 of culture, the Spirulina culture rotifers started to decline with significant reductions in % gravid. We also noticed the pH of the culture to also increase signficantly from the increased algae growth, perhaps leading to the culture decline.
Pinfish were found to be successfully reared on rotifers fed spriulina and spirulina utilized as greenwater. However the survival and general size appeared reduced compared to the controls. Future studies we would like to more specifically tailor incorporation of the diet utilizing known nutritional values of the cultured Spriulina, therefore conducting a more apples-to-apples comparison. Additional funding we have been successfully awarded, will allow us to conduct this furture experiment.
Hard clams supplemented with Spirulina were also found to have similar survival and growth, with Spirulina found within the clams guts. A future study within the same additional funding source will be conducted utilizing Spirulina nutritional analysis to more specifically plan and compare cutlure trials for clams.
Educational & Outreach Activities
Participation Summary:
Techniques for live Spirulina culture, performance metrics, and diatom nutrition variations with silica supplementation are being developed into white papers (from their current rough draft form) and will be distributed through Southern Regional Aquaculture Center extension services, Aquacontacts, the National Aquaculture Association (NAA) listservs, and minority aquaculture networks. Findings were presented at the Aquaculture Resource Council meeting in Florida and discussed at multiple World Aquaculture Society–affiliated roundtables. Outreach efforts have included over 10 social media posts shared via our platforms, the Florida Aquaculture Community (1.7k members), and AquaInfoExchange, as well as six educational tours of our facilities. Standard Operating Procedures (SOPs) are currently being finalized with stakeholder feedback and will be available for download on the Live Advantage Bait LLC website. Spirulina starter cultures have been offered for the past 18 months, and a vetted list of at least three commercial culture suppliers will be shared online to support broader industry adoption.
Learning Outcomes
In addition, over 20 aquaculture farmers have been personally toured, educated, and provided hands-on demonstrations on how to optimize microalgae culture techniques using marine Spirulina and enhanced diatom nutrition. These direct engagements have included on-site visits, tailored consultations, and technical training focused on improving live feed productivity, enhancing nutritional profiles, and increasing the consistency and resilience of microalgae cultures. Farmers received customized guidance on system design, silica supplementation strategies, and troubleshooting methods for maintaining optimal culture health. This peer-to-peer knowledge transfer approach has strengthened technical capacity across diverse farm operations and reinforced our commitment to practical, scalable solutions that benefit both small and large-scale producers.
Project Outcomes
One of the most critical insights from this project is the recognition of how microalgae nutritional profiles vary over time and under different culture conditions. This information is invaluable to hatchery operators and farmers, who must make daily decisions about feeding regimes and biomass production with limited predictive tools. By characterizing how species like marine Spirulina and diatoms respond nutritionally to changes in environmental parameters—such as silica availability, light, and harvest timing—this research empowers farmers to optimize feed quality and quantity, reducing waste and improving animal health outcomes.
Understanding and anticipating these nutritional fluctuations enables more precise management of live feed systems, which is directly tied to improved larval survival, growth rates, and cost efficiency in marine fish and shellfish hatcheries. As a result, this work contributes meaningfully to the economic and environmental sustainability of the aquaculture industry—particularly for species dependent on high-quality early nutrition.
Building on these findings, we have applied for a ~$50,000 grant from the Florida Aquaculture Resource Council to deepen our investigation into how microalgae optimization can enhance hatchery performance. This next phase will explore targeted feed trials and further refine standard operating procedures for scalable on-farm application, with the goal of creating resilient and nutritionally strategic live feed systems across Florida and beyond.
Building on the success of our initial Spirulina research, the next phase of this project will focus on evaluating a novel brackish-water strain of Spirulina for its nutritional profile and potential applications in commercial hatchery operations. This follow-up study will not only advance our understanding of the species' value but also rigorously test its effectiveness as a supplemental feed and water conditioner in both marine finfish and shellfish larval systems.
Project Objectives and Deliverables:
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Characterize the nutritional composition and physical properties of this newly isolated brackish Spirulina strain under varied environmental conditions.
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Conduct controlled larval rearing experiments using marine fish and clam larvae to assess Spirulina’s performance as a supplemental live feed, with special attention to survival, growth, stress resistance, and time to metamorphosis.
Anticipated Impact:
With climate change stress, inflationary input costs, and increasing international competition, Florida’s aquaculture producers must adopt more sustainable and resilient practices. By optimizing a low-cost, high-nutrient live feed that is adaptable to brackish conditions, this project offers scalable potential across species and production systems. Drawing on analogous benefits seen in poultry and freshwater aquaculture industries, we project that Florida’s aquaculture sector could realize a 10–15% reduction in operating costs, translating to a potential $10 million industry-wide savings. Benefits may include enhanced growth rates, improved survival, bolstered disease and stress resistance, and accelerated time to market—positioning Spirulina as a cornerstone of sustainable aquafeed strategies.