Dinoflagellates Reef Tank Complete Guide: Dino Identification

Snotty brown strings that rise and float at midday, then vanish by morning, almost never mean diatoms — that signature sequence is dinoflagellates, and they are genuinely dangerous to livestock. This dinoflagellates reef tank complete guide explains how to identify the strain, why Singapore reef tanks see dino outbreaks so often, and the practical three-step protocol that clears most cases in under a month. Gensou Aquascaping at 5 Everton Park treats dino consultations almost weekly, and the root cause is nearly always ultra-low nutrients combined with bleached RO/DI top-up.

Identifying Dinos vs Diatoms vs Cyano

Three brown slimes confuse beginners. Diatoms form a matte film that wipes easily and does not reattach. Cyanobacteria forms sheet-like mats with gas bubbles that release a distinctive earthy smell when disturbed. Dinos appear as brown strings with entrapped air bubbles, are slippery rather than matte, and often retract into sand or rock at night. The classic tell: the tank looks clean at 8am and terrible by 2pm.

Why SG Reefers See Dinos So Often

Singapore hobbyists over-engineer RO/DI purity and chase zero nitrate and zero phosphate as if those readings were goals. Combined with sparse early biodiversity and aggressive GFO dosing, the tank becomes a desert that only dinoflagellates can thrive in. Warm 26°C ambient water amplifies their reproduction rate. Most dino cases at Gensou start with a hobbyist reporting nitrate below the detection limit and phosphate at 0.00 ppm for weeks.

Strain Identification Under a Microscope

Not all dinos are equal. The common strains are Ostreopsis, Prorocentrum, Amphidinium and Coolia. A cheap USB microscope at SGD 45 on Shopee lets you look at a scrape drop at 200-400x. Amphidinium lives in sand and is hardest to clear. Ostreopsis and Prorocentrum swim in the water column and respond well to UV sterilisation. Knowing the strain shapes the battle plan significantly.

The Three-Day Blackout

The first intervention is a complete blackout — lights off, tank wrapped in a blanket or dark cloth, no feeding for three full days. Dinos are obligate photoautotrophs and collapse under sustained darkness far faster than corals. Most soft corals and LPS tolerate 72 hours of darkness without issue; skip the blackout only if you keep light-hungry SPS. Reopen to a dim 4-hour photoperiod on day four and ramp back over a week.

Dosing Nutrients Back In

Counterintuitively, dinos retreat when nitrate and phosphate rise. Target 5-10 ppm nitrate and 0.05-0.1 ppm phosphate. Dose sodium nitrate and potassium phosphate via Brightwell NeoNitro and NeoPhos, both stocked at Reef Depot at around SGD 45-55 per bottle. Feed the tank more generously — pellets twice daily, frozen mysis every other day. The goal is to reboot microbial diversity so competing organisms crowd out the dinos.

UV Sterilisation for Water-Column Strains

A properly sized UV steriliser at 1 watt per 3-4 litres, fed through a slow pump at around 400 litres per hour, is devastating to swimming dinos. Aqua UV and Pentair units in the SGD 180-350 range handle nano and mid-sized reefs. Run UV continuously for 2-3 weeks during active outbreak, then reduce to daytime only. Amphidinium in sand ignores UV, so this only solves the floating strains.

Microbial Seeding for Competition

Dosing live bacteria rebuilds the biodiversity lost to ultra-low nutrient keeping. DrTim’s Waste Away, MicroBacter7 and Fritz Turbo Start are all available at local reef shops for SGD 35-60. Dose nightly for two weeks. Pairing bacterial dosing with a small bottle of Tisbe pods from Algagen — Reef Depot stocks these at SGD 55 — restocks grazers that consume dino biofilm. The one-two punch works better than either alone.

Physical Removal During the Fight

Siphon visible dino masses out daily using a turkey baster and filter sock combination. Never wipe and let debris settle — that just seeds new patches. Change filter socks every 24 hours at the outbreak peak. A fine 100-micron sock traps individual cells that a 200-micron sock misses. Expect to go through a dozen socks in the first fortnight; budget SGD 4-6 per sock.

What to Avoid During Treatment

Do not run GFO or phosphate remover — you want nutrients elevated, not stripped. Skip large water changes, which reset the bacterial populations you are trying to build. Avoid adding new corals or fish until dinos are visibly gone for 2-3 weeks. Hydrogen peroxide dosing works for some strains but kills soft corals if overdosed; leave it as a last resort under guidance. Early over-treatment often extends the outbreak by weeks.

Preventing Recurrence

After clearing, hold nutrients at 2-5 ppm nitrate and 0.03-0.08 ppm phosphate permanently. Feed the tank rather than starving it. Seed pods and bacteria quarterly as insurance. Keep a diverse CUC — Cerith, Nassarius, Trochus, a few Nerites — rather than a monoculture. Outbreaks recur most often when a hobbyist panics about slightly elevated nitrate and strips it back to zero, restarting the cycle.

Related Reading

• Diatoms Reef Tank Complete Guide
• Reef Tank Uglies Stage Complete Guide
• Reef Tank UV Sterilizer Beginner Guide
• Reef Tank Parameters Beginner Guide
• Copepods Reef Tank Beginner Guide