🟤 Diatoms (Brown Algae)

Diatoms are single-celled algae that commonly appear as a brown, dusty coating in new aquariums. Often called "brown algae" (though technically not algae), diatoms are a normal part of the tank cycling process and typically resolve on their own within a few weeks. While unsightly, they're generally harmless and indicate your tank is maturing.

📋 Quick Facts

Type	Siliceous microalgae (Bacillariophyta)
Appearance	Brown, dusty coating on surfaces
Severity	Low - Normal in new tanks, self-resolving
Common Causes	New tank, silicates, low light
Treatment Difficulty	Easy - Usually resolves naturally

🔍 Identification

Diatoms have distinctive characteristics:

Brown color - Tan to dark brown coating
Dusty texture - Easily wipes off, not slimy
Covers everything - Glass, rocks, sand, equipment
No smell - Unlike cyanobacteria
Returns quickly - Wipes off but grows back (initially)
Appears in new tanks - Common 2-8 weeks after setup

Diatoms vs. Similar Problems

Feature	Diatoms	Cyano	Dinoflagellates
Color	Brown/tan	Red/maroon	Golden brown
Texture	Dusty, powdery	Slimy sheets	Snotty, stringy
Smell	None	Musty/earthy	None to mild
Wipes off	Clean, easy	Peels in sheets	Stringy residue
When appears	New tanks	Any time	Low nutrient tanks

⚠️ Common Causes

New tank syndrome - Normal part of cycling/maturation
Silicates - Diatoms use silica to build shells
Tap water - Contains silicates
New sand - Can leach silicates
Low competition - No established organisms to compete
Excess nutrients - New tank hasn't balanced yet

💊 Treatment Options

1. Wait It Out (Best Approach)

For new tanks, diatoms typically resolve naturally:

Usually clears within 2-6 weeks
As silicates are consumed, diatoms decline
Tank biology matures and outcompetes diatoms
No intervention needed in most cases

2. Clean-Up Crew

Snails readily consume diatoms:

Trochus snails - Excellent diatom grazers
Cerith snails - Work on sand and rocks
Nerite snails - Great glass cleaners
Nassarius snails - Stir sand, eat diatoms
Astrea snails - Good all-around grazers

3. Reduce Silicates

Use RODI water (not tap water)
Run GFO (some types absorb silicates)
Use silicate-removing media
Rinse new sand thoroughly before adding

4. Manual Removal

Wipe glass with algae scraper
Vacuum sand surface during water changes
Turkey baster to blow off rocks
Not necessary, but improves appearance

5. Increase Light (Carefully)

Diatoms prefer low light conditions
Higher light favors other organisms
Don't overdo it - can trigger other algae
Gradual increases recommended

⏱️ Timeline in New Tanks

Week	What to Expect
1-2	Tank cycling, may see first diatoms
2-4	Diatom bloom peaks
4-6	Diatoms begin declining
6-8	Most diatoms cleared
8+	Tank stabilized, diatoms rare

🛡️ Prevention

Use RODI water - Eliminates silicates from source
Rinse new sand - Removes excess silicates
Proper cycling - Allows biology to establish
Add snails early - Provide grazing pressure
Patience - New tanks go through phases

❌ Common Mistakes

Panicking over normal new tank diatoms
Using tap water (contains silicates)
Excessive cleaning that disrupts cycling
Confusing diatoms with more serious problems
Chemical treatments (unnecessary)
Giving up on tank thinking something is wrong

❓ When to Be Concerned

Diatoms in established tanks (6+ months) may indicate:

Silicates in water source - test and address
New sand or rock added - temporary
Die-off event releasing nutrients
May actually be dinoflagellates (check carefully)

📚 Summary

Diatoms are a normal, expected phase in new aquariums and rarely cause long-term problems. The brown dusty coating is unsightly but harmless, and will naturally resolve as your tank matures and silicates are depleted. Adding a good snail cleanup crew speeds the process. Use RODI water to prevent silicate introduction, and resist the urge to over-clean or chemically treat. Within a few weeks, diatoms typically become a distant memory. If diatoms appear in an established tank, investigate the cause but don't panic - they're still easy to address.

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