Keeping a log of your algae culture means writing down a few facts every day: date, temperature, colour, smell, what you added and what you took out. It takes under a minute, and it turns a mysterious crash into something you can trace. When a culture fails, the log shows what changed before it did; when it thrives, it shows you how to repeat it.
Why memory is not enough
Algae cultures change slowly and fail quickly. A jar that looked fine on Tuesday can be brown by Friday, and by then you will not remember whether you changed the lamp, added fertiliser or moved the jar. Without written notes, every failure looks like bad luck, and you repeat it. With notes, a pattern appears: crashes follow heat waves, or cloudy mornings follow a double dose of nutrients.
What to record
| Field | Example | Why |
|---|---|---|
| Date and time | 12 Oct, 18:00 | Lets you see rates of change |
| Culture / jar ID | Chlorella B | Separates different jars |
| Temperature | 27 °C | The single biggest driver |
| Colour (1 to 5) | 4, bright green | Tracks density |
| Smell and clarity | Fresh, clear | Early warning for bacteria |
| Added or removed | +10 mL nutrients, −200 mL harvested | Explains jumps |
| Notes | Moved to new shelf | Anything unusual |
Optional extras are pH, a photo of the jar against a white card, and cell counts if you have a microscope. A photo each day in the same spot is a surprisingly good record of density.
Keep one page per jar
Use a notebook, a spreadsheet or a note on your phone, but keep one page or tab per jar. Label the jar with the same ID. If you split a culture, note the parent and the date of the split, so that you can follow a lineage. See how to split and scale up.
Using the log when something goes wrong
- Find the last day the culture looked good.
- Look at every entry between that day and the first sign of trouble.
- Check temperature first, then any additions, then any change in light or position.
- Test your idea on the reserve jar before changing everything.
A log also answers the question people ask most often: how long should it take to reach full density? After a couple of batches, you will have your own figure for your own conditions.
Logging when feeding live food
If your algae feed Daphnia, rotifers or fish, add two more fields: how much algae went to each, and how the animals responded in the next day or two. That link between feed and result is what lets you adjust amounts sensibly. See culturing live food for your aquarium fish and how to tell if your algae culture is healthy for what to look for.
A template you can copy
This layout fits a notebook page or a spreadsheet. One line per observation, one block per jar.
| Date | Jar | Temp | Colour 1 to 5 | Smell | Action | Notes |
|---|---|---|---|---|---|---|
| 3 Oct | C1 | 26 | 2 | Fresh | Started from C0, 250 mL into 750 mL | Window shelf |
| 5 Oct | C1 | 27 | 3 | Fresh | +5 mL nutrient mix | |
| 8 Oct | C1 | 29 | 4 | Fresh | Harvested 200 mL for Daphnia | Warm day |
| 11 Oct | C1 | 31 | 3 | Slightly sour | Moved away from window | Heat spike? |
| 12 Oct | C1 | 27 | 3 | Fresh | Water top-up | Recovering |
Even this tiny record shows that the culture dipped after a warm day by the window and recovered after being moved. Without it, you might blame the nutrients.
What the log lets you answer
- How long does a new jar take to reach full colour? Look at your last three batches.
- How much can I harvest and keep density? Compare harvest volumes with the colour score a few days later.
- Which jar is the healthiest lineage? Trace parent-child relationships and compare.
- Did a change help? A new lamp, medium or position becomes a clear before and after.
Keeping the habit
- Put the notebook where you check the jar, not in a drawer.
- Write the entry at the same time as the check; it takes seconds.
- Use abbreviations and numbers, not sentences.
- Photograph the jar next to the entry once a week.
- Once a month, read back the last month and note one thing to change.
Logging for animals that eat the culture
When algae feed Daphnia, rotifers, shrimp or fish, record three more things: how much algae each received, any sign of a problem such as sluggish animals or cloudy water, and anything you changed in the animal tank. A few weeks of these entries show which algae batch correlates with a good response, and they let you spot slow declines before they become crashes. The overall approach is in culturing live food for your aquarium fish, and the daily check is explained in how to tell if your algae culture is healthy.
For classrooms and groups
A shared log is a good way to teach scientific method. Students record the same measures, compare jars that differ in a single variable such as light or temperature, and draw conclusions from their own data. A simple controlled comparison, for example two jars with different photoperiods, makes a good project and fits the template above.
Common questions
How long should I keep records?
At least until a culture is retired. Keeping the log of a successful batch is useful when you start another one.
Is a spreadsheet better than paper?
It is easier to chart, but paper next to the jar is more likely to actually get used.
What is the most useful single field?
Temperature. It explains more crashes than anything else.
Should I record pH?
If you have a test kit, yes, once a week. It is especially useful for Spirulina, where staying above pH 9 matters.
Can I use an app?
Any notes app or spreadsheet works. Choose the one you will open every day.
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