Algae guide
Diatoms (Brown Algae) in Aquarium: Causes and How Long It Lasts
Last updated: May 2026
Quick summary
- What it is: Single-celled silica-armoured microalgae that dust leaves, driftwood and glass in young aquaria.
- Severity: 1 / 4 — Benign nuisance coating during maturation windows
- Primary cause: Silicates leaching from substrates or tap chemistry until biofilms competitively shade them out.
- Primary fix: Patience, nerite/Otocinclus grazing, polishing glass—skip snake-oil cures that trade cash for ammonia spikes.
What hobbyists observe
Dull cocoa film easily wiped returning overnight on lower energy scapes lacking mature biofilm grazing pressure.
Self-limiting arcs
Most enclosures clear within roughly two lunar maintenance cycles once silicates deplete—swapping aggressively to bottled minerals without testing simply shifts the bottleneck.
Run our free aquarium stocking calculator before adding six Otocinclus “cleanup crews” onto immature rigs.
When algae eaters genuinely help
Nerites scour glass ridges; juvenile Otos graze slime yet demand established oxygen curves—purchase only on scrupulously clean supplier runs.
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