Cloudy Aquarium Water — Deep-Dive Diagnosis & Fixes

💧 Cloudy Aquarium Water — Deep-Dive Diagnosis & Fixes

⚪ Milky/White Haze
- Bacterial bloom (heterotrophic) after overfeeding, deep cleaning, new tanks, or a mini-cycle.
- Mineral precipitation “snowstorm” (calcium carbonate) after buffers/mineral salts.
🟢 Green Water
- Free-floating algae (not on glass/leaves only).
🤍 Grey/Tan Particulate
- Unrinsed substrate, rock dust, stirred detritus; also diatom dust (silicates) in new tanks.
🤍💨 Microbubbles
- Tiny bubbles from air leaks, venturi, degassing tap/well water.
🟤 Tea/Amber Tint
- Tannins from wood/leaf litter (color, not true cloudiness).

💨 Ammonia: 0 ppm
💨 Nitrite: 0 ppm
💧 Nitrate: <20–40 ppm (aim closer to 20; <10 for fry/discus/shrimp)
⚖️ pH/KH/GH: Stable (KH ≥3 dKH for most community tanks)
🌡️ Temperature: Stable for species
📈 Phosphate/Silicate (optional): High PO₄ fuels green water; SiO₂ drives diatoms

📝 Tip: Log values. Trends beat snapshots.

🕒 New tanks: This is often cycling—3–7 days to self-clear once bacteria balance.
🍽️ Reduce organics: Cut feeding 30–50%; remove leftovers.
🧽 Biofilter first: Never replace all media at once; rinse gently in tank water only.
💨 Boost O₂: Blooms burn oxygen—add airstone/surface ripple (especially at night).
🔁 Water changes: 20–30% every 2–3 days only if ammonia/nitrite appear.
🧪 Bacteria-in-a-bottle: Can speed recovery after a filter shock.
🚫 Avoid flocculants as a first step; fix the cause (excess organics).

Red flags that caused it: overcleaned filter; washed media under tap (chlorine); heavy substrate stir; big bioload jump.

🧂 Triggered by adding buffers/mineral salts into high-pH/high-KH water or mixing products.
🔬 Test KH/GH; if very high, slow down dosing and pre-dissolve additives.
💧 Perform small water changes; switch to remineralized RO/DI if needed.
⚖️ Dose buffers to target values, not by habit; avoid mixing brands that overlap.

💡 Light: Cap at 6–8 h/day; eliminate direct sun; use a timer.
🌑 Blackout: 72 hours (cover tank; keep filter/aeration running) → 40–50% water change → resume short photoperiod.
🔦 UV Sterilizer: Extremely effective.
- Run slower flow through the UV (longer dwell time) for green water clarity.
- Plumb UV after mechanical filtration for best contact.
🌱 Compete with plants: Floaters (salvinia, frogbit) + fast stems absorb excess nutrients.
🧪 Nutrient control: Keep nitrate <20–30 ppm; keep phosphate modest; reduce heavy feeding.

🚿 Thoroughly rinse substrate until water runs clear before use.
🧊 Add polishing media: fine filter floss or 5–50 micron pads short-term (remove once clear).
🌊 Flow tuning: Angle returns to avoid sandstorms; use prefilter sponges on intakes.
🧽 Staged cleaning: Light vacs over several days > one deep, detritus-bombing clean.

🔍 Seal checks: Reseat canister O-rings, tighten hose clamps; inspect intake for pinholes.
💧 Degas new water: Aerate/heater in the change bucket 30–60 min before adding (well water often gas-supersaturated).
🔄 Return direction: Aim outputs to break bubbles before the viewing pane; reduce venturi draw.

✅ Harmless/beneficial for many soft-water fish; mild antimicrobial, reduces stress.
🧺 Activated carbon / Purigen to polish if you want clear water.
🪵 Pre-soak/boil new wood; routine 20–30% weekly changes lighten tint.

🔁 Turnover: Aim 4–8× tank volume/hour total flow (more for river fish; less for bettas).
🧽 Prefilter sponge on intakes catches gross debris → cleaner canister internals.
🧊 Mechanical stages: Coarse → medium → fine (floss/micron); fine is temporary.
🧱 Chemical media:
- Carbon/ROX for tannins/organics (swap ~4–6 weeks).
- Purigen for water polish/regeneration option.
- GFO (iron media) if phosphate chronically high (use sparingly; monitor).
🔦 UV sterilizer: Best long-term for recurrent green water/bacterial haze; match manufacturer’s wattage & GPH for algae (slower is better).

If your tank produces ~20 ppm nitrate/week:
- 50% weekly keeps the swing roughly ~20→40 ppm.
- 25% weekly lets it climb ~45→60+ ppm.
- 👉 Adjust water-change % to your nitrate production rate.

🧪 Test: NH₃/NH₂ must be 0 → if not, water change + aeration immediately.
👀 Color check:
- ⚪ Milky → bacterial or mineral; check cleaning habits & KH/GH.
- 🟢 Green → light/nutrients; blackout + UV.
- 🤍 Dust → polishing floss + flow fixes.
- 🤍💨 Bubbles → seal/degassing.
- 🟤 Tint → tannins; optional carbon.
🔁 Adjust feeding, flow, filtration; avoid overcleaning bio media.
📓 Log results; tweak routine.

Daily: Quick glance, remove leftovers, confirm strong surface ripple.
Weekly: 20–50% water change (per your nitrate rate), light substrate vac, glass wipe.
Monthly: Rinse prefilter and mechanical pads in tank water; swap carbon if used.
Quarterly: Deep equipment inspection, hose clean, impeller check, UV sleeve/quartz cleaning.

🧪 Old Tank Syndrome: Very high nitrate + low KH → pH crash risk. Fix with gradual changes over days; re-buffer slowly.
☠️ Filter crash (after meds/chlorine): Add bottled bacteria; tiny feedings; frequent testing.
🪸 Diatoms (brown dust): Early silica bloom; usually clears in weeks; oto cats/nerite snails help; silicate resin if your tap is high.
🧪 Clarifiers/flocculants: Can clump fines for removal but sometimes drop O₂—aerate well and use sparingly.

Clarity comes from biology + mechanics + habits working together. Fix the root (organics, light, flow), not just the symptom.

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