Infusoria is the essential first food for tiny fry that are too small to eat baby brine shrimp or other live foods. Whether you're breeding bettas, gourami, tetras, or other egg-layers, this complete care guide will show you exactly how to culture, feed, and maintain healthy infusoria populations for your newborn fish.
What Is Infusoria?
Infusoria is a collective term for microscopic freshwater organisms such as ciliates, flagellates, rotifers, and other microfauna. These tiny organisms are essential for feeding newborn fry, shrimp larvae, and other small aquatic animals that cannot eat larger foods.
What aquarists use infusoria for:
- feeding tiny fry (bettas, gourami, tetras, rasboras, killifish)
- supporting shrimp larvae
- boosting microfauna in planted tanks
- starting natural ecosystems
- feeding copepods and other small cultures
How to Use Infusoria for Fry
Infusoria is the first food for many species of fry that are too small to eat baby brine shrimp or microworms.
What Eat Infusoria?
- Betta fry
- Gourami fry
- Tetra fry
- Rasbora fry
- Cichlid fry
- Shrimp larvae
- Nano fish fry
How to Feed
- Add a small amount of infusoria directly to the fry tank.
- Repeat 3-5 times daily.
- Add more when the water clears.
- Stop feeding once fry can eat larger foods (usually 3–7 days).
Signs Fry Are Eating Infusoria
- Fry have round, full bellies
- They cluster near the water surface
- They show increased activity
What Infusoria Eat — Best Food Sources
Infusoria feed on bacteria and microscopic particles.
Best Foods
- Chlorella or Tetraselmis
- Green water
- Indian almond leaves
- Mulm from a healthy tank
- A small piece of lettuce or spinach
- A tiny piece of banana peel
- A tiny piece of potato
Feeding Tips
- Use tiny amounts — too much causes foul smells.
- Replace food when it breaks down completely.
- Cultures should smell earthy, not rotten.
How to Harvest Infusoria Safely
- Use a pipette, syringe, or turkey baster
- Draw from the middle layer (densest zone)
- Avoid sucking up debris from the bottom
- Add directly to fry tanks, or filter through filter floss
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How to Culture Infusoria at Home (Full Step‑by‑Step Guide)
Culturing infusoria is simple, low‑maintenance, and perfect for fry emergencies.
What You Need
- A clean jar or container (8–32 oz)
- Your starter infusoria culture
- Dechlorinated water, or seasoned tank water
- A food source (leaf, veggie, or microalgae)
- Indirect light
Step‑by‑Step Instructions
- Fill your container with water.
- Add your starter culture (10–40% of the total volume).
- Add a food source.
- Place in indirect light — not direct sun.
- Wait 1–3 days for the culture to bloom.
- Harvest lightly using a pipette or turkey baster.
- Top off with fresh water as needed.
How to Tell When Your Culture Is Ready
- Water becomes slightly cloudy or milky
- A faint earthy smell (not rotten)
- Fry respond well when fed
How Often to Harvest or Restart
- Harvest daily once the culture is active
- Restart the culture every 1–2 weeks for best results
- Keep multiple jars going for reliability
Tips for Success
- Avoid overfeeding the culture
- Keep temperature stable
- Use clean equipment
- Shake gently to resuspend organisms
- Start new jars regularly
Troubleshooting Infusoria Cultures
Culture Smells Rotten
- Too much food
- Food decomposed too quickly
- Restart with less food
Water Is Clear, No Bloom
- Not enough food
- Too cold
- Not enough light
- Culture is old — restart
Culture Turns Brown
- Food source exhausted
- Culture aging out
- Restart with fresh water and food
Fry Aren’t Eating
- Add more infusoria
- Feed smaller amounts more often
- Ensure water flow isn’t too strong
Infusoria FAQ — Answers to Common Questions
What is infusoria used for?
Feeding tiny fry, shrimp larvae, and microfauna that cannot eat larger foods.
How long does infusoria last?
Cultures stay productive for 1–2 weeks before needing a restart.
How often should I feed infusoria to fry?
3-5 times daily until fry can eat larger foods.
Can infusoria live in a fish tank?
Yes — but populations stay low unless food is abundant.
Does infusoria make water cloudy?
A little cloudiness is normal and safe for fry.
Can I overfeed infusoria to fry?
No — infusoria does not foul water the way larger foods do.
Why does my infusoria smell bad?
Too much food or decomposition. Restart the culture.
How do I know if my culture is ready?
Cloudy water, earthy smell, and visible micro‑movement under light.
Can I use Chlorella or Tetraselmis to feed infusoria?
Yes — both are excellent food sources.
How long do infusoria live?
Individual organisms live days to weeks, but cultures renew continuously.
Should I keep multiple infusoria cultures?
Yes — recommended for reliability.
Can infusoria survive cold water?
Yes, but growth slows significantly.
Do I need aeration?
No — infusoria thrive in still water.
Can I use tank water to start infusoria?
Yes — mulm and biofilm help jump‑start the culture.