Aquarium Biofilm: What It Is and Why Shrimp Love It
Table of Contents
- What Is Biofilm?
- Why Biofilm Matters for Shrimp and Fry
- How Biofilm Forms
- How to Encourage Biofilm Growth
- White Biofilm on New Driftwood
- Biofilm vs Bacterial Bloom
- Why New Tanks Lack Biofilm
- Frequently Asked Questions
What Is Biofilm?
Biofilm is the thin, often invisible layer of microorganisms coating virtually every surface in a mature aquarium. It is composed of bacteria, microalgae, fungi, protozoa, and the polysaccharide matrix they produce for anchorage. Run your finger along the inside glass of an established tank and you will feel a slight sliminess — that is biofilm.
In the wild, biofilm blankets every submerged surface. It is the base of the food chain for many small aquatic organisms and absolutely essential for shrimp colonies and fish fry. Despite this importance, biofilm rarely gets discussed in aquarium guides. At Gensou, we consider biofilm development a critical step in tank maturation, particularly for the shrimp tanks we set up at our 5 Everton Park studio.
Why Biofilm Matters for Shrimp and Fry
Watch healthy shrimp and you will notice they spend most of their day grazing — front appendages constantly picking at surfaces. What they are eating is largely biofilm, which provides:
- Continuous nutrition: Unlike pellet foods consumed in minutes, biofilm is always available for 24-hour grazing.
- Complete nutrition: Microorganisms provide proteins, carbohydrates, fats, vitamins, and minerals in a naturally balanced form.
- Essential food for shrimplets: Baby shrimp are too small for commercial foods during their first weeks. They depend almost entirely on biofilm. A tank without adequate biofilm sees high shrimplet mortality even when adults appear healthy.
Many fish fry similarly graze on biofilm during their earliest days. Otocinclus catfish, a popular algae eater in Singapore planted tanks, also rely heavily on biofilm throughout their lives.
How Biofilm Forms
- Surface conditioning (hours): Dissolved organic molecules adhere to newly submerged surfaces.
- Primary colonisation (days): Bacteria attach and begin multiplying, producing the sticky matrix that forms the structural base.
- Community development (weeks): Microalgae, diatoms, protozoa, and fungi join the community. Biofilm becomes more complex and nutritious.
- Maturation (months): A stable, self-sustaining community that is constantly grazed and regrows.
This is why experienced shrimp keepers insist on aging tanks for 6-8 weeks before adding shrimp. The cycling process handles ammonia and nitrite, but biofilm needs additional time to develop into a robust food source.
How to Encourage Biofilm Growth
Driftwood
Natural wood is one of the best biofilm substrates. The rough, porous surface provides enormous surface area for microbial colonisation. Malaysian driftwood, Mopani, and Spider wood are popular choices in Singapore.
Indian Almond Leaves (Catappa)
Dried catappa leaves decompose slowly over 4-6 weeks, releasing tannins and organic compounds that feed biofilm bacteria. Shrimp graze on both the leaf and the biofilm growing on it. Add 1-2 leaves per 20 litres, replacing as they decompose.
Mulberry Leaves
Decompose somewhat faster than catappa and are rich in nutrients that promote biofilm growth. Widely available from Singapore aquarium shops and online sellers.
Other Biofilm-Promoting Surfaces
- Lava rock: Extremely porous, massive surface area for colonisation.
- Cholla wood: Honeycomb structure provides shelter and grazing surfaces. Very popular in Singapore shrimp tanks.
- Sponge filters: Thick biofilm develops on the sponge that shrimp actively graze.
- Moss: Java Moss, Christmas Moss, and other mosses provide enormous surface area for biofilm.
Commercial Products
- Bacter AE: Powdered supplement that feeds biofilm-producing bacteria. Extremely popular in the shrimp hobby. Dose sparingly — over-dosing can deplete oxygen in small tanks.
- SL-Aqua Purify: Promotes beneficial bacterial growth on surfaces.
White Biofilm on New Driftwood
The white, fuzzy growth appearing on new driftwood within days of submersion is one of the most common questions we receive at Gensou. This is a completely harmless bacterial biofilm.
When new wood is submerged, it releases sugars and organic compounds. Bacteria rapidly colonise these nutrients, forming a visible white or grey fuzzy layer. Key points:
- Completely harmless. Will not affect fish, shrimp, or water parameters.
- Temporary. Disappears on its own in 2-6 weeks once bacteria exhaust the available nutrients.
- Shrimp and snails love it. They graze on it enthusiastically.
- Do not scrub it off. It will simply return. Allow it to run its course.
Biofilm vs Bacterial Bloom
It is important to distinguish beneficial surface biofilm from a harmful bacterial bloom in the water column.
| Feature | Biofilm (Beneficial) | Bacterial Bloom (Potentially Harmful) |
|---|---|---|
| Location | On surfaces (glass, wood, rocks) | Suspended in water column |
| Appearance | Thin film on surfaces | Cloudy, milky water |
| Effect | Beneficial food source | Can deplete oxygen |
| Duration | Permanent (self-sustaining) | Temporary (days to weeks) |
| Action | Encourage it | Reduce feeding, water changes |
A bacterial bloom turns the entire tank cloudy, usually from an ammonia spike, overfeeding, or an unstable new tank. A severe bloom can deplete dissolved oxygen — especially dangerous in warm Singapore tanks (28-32 degrees) where oxygen is already lower. Reduce feeding, perform partial water changes, and ensure adequate aeration.
Why New Tanks Lack Biofilm
Every new aquarium starts biologically sterile. While nitrogen cycle bacteria establish within 4-6 weeks, the broader biofilm community takes significantly longer to mature. This is why shrimp keepers see high shrimplet mortality in tanks less than 3 months old — parameters may be perfect on paper, but the food source baby shrimp need has not developed yet.
Practical implications for Singapore hobbyists:
- Allow your shrimp tank to run 6-8 weeks minimum before adding livestock.
- Add biofilm sources (driftwood, catappa leaves, mulberry leaves) from day one.
- Transfer mature sponge media from an established tank if available.
- Use biofilm supplements like Bacter AE sparingly in new setups.
- Do not scrub all surfaces during maintenance — clean front glass for viewing but leave back glass and hardscape untouched.
Frequently Asked Questions
Is the slime on my driftwood biofilm or algae?
White or grey fuzzy growth on new wood is bacterial biofilm — harmless. Green growth is algae. Brown growth may be diatoms or biofilm with a diatom component. All are safe for livestock and shrimp will graze on them. The only growth to watch for is blue-green cyanobacteria, which forms slimy, foul-smelling sheets on the substrate.
Can I have too much biofilm?
Surface biofilm is rarely problematic. However, heavy supplementation with products like Bacter AE can temporarily reduce dissolved oxygen, particularly in small, warm tanks. In Singapore’s 28-30 degree conditions where oxygen is already lower, dose cautiously and ensure adequate surface agitation.
Why do my shrimp ignore commercial food but graze constantly?
This is perfectly normal and indicates good biofilm development. Shrimp are natural grazers whose primary wild food source is biofilm. They will always prefer grazing over eating pellets. Offer commercial food in small quantities 2-3 times weekly as a supplement, not the primary diet.
Want to create the ideal shrimp environment? Visit us at Gensou, 5 Everton Park, Singapore. Over 20 years of shrimp keeping and aquascaping experience. Contact us for expert advice on building a mature, biofilm-rich tank.
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