Small-scale algae production for a hatchery comes down to one idea: always have the next, larger culture ready before the previous one is used. Algae are made in stages, from a small starter jar to a 10 or 20 litre carboy and then to a production tank, so that something healthy is available every day. The system works when it is boring: same containers, same medium, same routine, same records.
The culture stages
| Stage | Volume | Purpose |
|---|---|---|
| Stock | 50 to 250 mL | Clean reserve kept under gentle light; the source for everything else |
| Starter | 1 to 2 L | Bulk-up of cells to inoculate the next stage |
| Intermediate | 10 to 20 L | Volume to seed or feed production |
| Production | 50 L and up | Feed for rotifers, Daphnia, larvae or tanks |
Each step is inoculated with about 10 to 20% of its volume from the stage before. The ratios are the same as described in how to split and scale up.
Batch versus semi-continuous
- Batch: fill, inoculate, grow, harvest everything, sterilise and start again. It is simple and clean, and suits the early stages.
- Semi-continuous: harvest part (for example one third to one half) every day or two and refill with fresh medium. It gives steady output and needs fewer restarts, but needs more care to avoid contamination over time.
Small operations often use a mix: batch for the stock and starter, semi-continuous for production tanks, with a restart every few weeks.
A weekly routine
- Daily: look, smell, check temperature, log colour and density, harvest what is needed.
- Every 2 to 3 days: replace harvested volume with fresh medium.
- Weekly: inoculate a fresh container from stock, clean one old container and check pH.
- Monthly: replace the stock culture from a clean source or fresh starter.
Where it usually goes wrong
Most failures in small hatcheries are one of three things: contamination, too much heat or running out of the next stage. All three are preventable.
- Contamination spreads through shared tools and open lids. Use a separate pipette or cup for each container. See preventing contamination.
- Heat damages cultures by the lamp rack. Monitor temperature as described in temperature control.
- Timing: not having a larger culture ready forces use of a weak one. Scheduling avoids that.
Record everything
A culture log that records the date, volume, temperature, medium batch and observations makes it possible to trace problems to a cause. Our article on logging has a simple layout.
What it feeds
Production algae go to rotifers, Daphnia, brine shrimp and, directly, to larval tanks as green water. See feeding rotifers with Chlorella and green water in larval rearing.
For small scale work, a live Chlorella vulgaris or Spirulina platensis starter is the usual entry point.
Sizing the system from the demand
Plan backwards from what you need. Suppose a hobby breeding room feeds 3 litres of rotifer culture and four small fry tanks with green water each day.
- Daily algae demand. About 100 to 150 mL of dense Chlorella for the rotifers, and 50 mL per fry tank, so roughly 300 to 350 mL per day.
- Production tank volume. If you harvest a third of the volume each day, a 1 litre production culture supplies about 330 mL. Add a safety margin of 50% and plan for 1.5 to 2 litres in the production stage.
- Intermediate stage. It needs to supply the production stage every 3 to 4 weeks, so a 5 litre intermediate culture is plenty.
- Starter and stock. A 250 mL stock and a 1 litre starter cover the rest.
This is a small system, but the logic is the same at 100 times the scale.
A layout that works in a small room
- Stock shelf: small flasks under a dim LED, at 20 to 24 °C, cleaned and replaced monthly.
- Starter and intermediate shelf: bright, with aeration and a timer.
- Production shelf: the largest vessels, with aeration, a thermometer and an easy way to draw off the culture, such as a tap near the bottom.
- Clean zone: a table with a tray for tools, and a bottle of dilute bleach and rinse water.
Cleaning and changeover
| Task | Frequency |
|---|---|
| Wipe shelves and lamp surfaces | Weekly |
| Disinfect and rinse production vessels | At each restart, about every 3 to 4 weeks |
| Replace air tubing and stones | Every few months or when slimy |
| Replace the stock culture | Monthly |
| Calibrate or check the thermometer | Every few months |
When to scale beyond a hobby system
Signs that you have outgrown the simple approach include needing more than a few litres of algae per day, depending on the system for income or research, or wanting to feed multiple species reliably. At that stage, consider a dedicated room with temperature control, filtered air, and a few standard media; consult hatchery manuals such as those published by FAO for live feed production. Even so, the stage logic and the discipline of logging remain the same, as described in the culture log guide.
Common questions
How much algae does a small hatchery need?
That depends on the number of rotifers or larvae, but it is usually measured in litres per day, not millilitres. Plan the production stage for at least a few times your daily use.
Do I need a laboratory?
No. A clean shelf, a lamp rack, covered containers and a routine are enough for small-scale operations.
How often should I restart the stock?
Every few weeks, or whenever you see anything unusual in a sample.
Can I run all stages in one room?
Yes, but keep the stock culture apart from the production stage and handle it first, so you do not carry contamination from large vessels to the clean ones.
Is aeration needed in every stage?
Not in the stock flasks, where gentle shaking is enough. Starter and larger stages benefit from gentle bubbling.
Ready to grow your own?
Live starter cultures, grown with care and shipped ready to thrive.
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