Water Quality Cheat Sheet - Tropical Crayfish

Quick Reference Table

All parameters at a glance — ideal, acceptable, and danger ranges.

Parameter	Formula	Ideal	Acceptable	Danger Zone	Test Frequency
🌡️ Temperature	°C	24–28°C	20–32°C	<15°C or >35°C	2× daily
⚗️ pH	—	7.0–8.5	6.0–9.0	<6.0 or >9.0	Daily
💨 Dissolved Oxygen	mg/L	6–8 mg/L	4–6 mg/L	<4 mg/L	2× daily (AM/PM)
☠️ Ammonia (Total NH₃/NH₄⁺)	mg/L	<0.5 mg/L	0.5–1.0 mg/L	>1.0 mg/L	Daily
⚡ Nitrite (NO₂⁻)	mg/L	<0.1 mg/L	0.1–1.0 mg/L	>1.0 mg/L	Daily
🧪 Nitrate (NO₃⁻)	mg/L	<10 mg/L	<30 mg/L	>50 mg/L	Weekly
🧂 Alkalinity	mg/L CaCO₃	100–200	50–100 (>200 high)	<50	Weekly
🪨 Hardness	mg/L CaCO₃	100–200	>50	<20	Weekly
🌊 Salinity	ppt	0–1 ppt	0–5 ppt	>10 ppt	Weekly
👁️ Turbidity (Secchi)	cm	30–50 cm	15–80 cm	<10 cm	Daily
🔋 Carbon Dioxide	mg/L	<5 mg/L	<15 mg/L	>25 mg/L	As needed

Parameter Deep Dive

Detailed breakdown of each critical parameter with action thresholds.

🌡️ Temperature

Ideal

24–28°C

Acceptable

20–32°C

Danger

<15°C / >35°C

Why it matters: Controls metabolism, growth rate, molting frequency, and oxygen solubility.
Test at: Same time daily (AM and PM).
Quick fix: Add shade in summer; use deeper ponds for thermal buffering.

⚗️ pH

Ideal

7.0–8.5

Acceptable

6.0–9.0

Danger

<6.0 / >9.0

Why it matters: Affects ammonia toxicity (more toxic at high pH), enzyme function, and mineral availability.
Test at: Daily, ideally morning and evening.
Quick fix: Add lime (CaCO₃) to raise; use acid buffering for high pH.

💨 Dissolved Oxygen (DO)

Ideal

6–8 mg/L

Acceptable

4–6 mg/L

Danger

<4 mg/L

Why it matters: Most critical parameter. Low DO causes stress, reduced feeding, and mass mortality within hours.
Test at: Dawn (lowest point) and mid-afternoon (highest point).
Quick fix: Turn on aerators immediately; perform 30% water exchange.

☠️ Ammonia (Total NH₃/NH₄⁺)

Ideal

<0.5 mg/L

Acceptable

0.5–1.0 mg/L

Danger

>1.0 mg/L

Why it matters: Toxic to crayfish gills. Toxicity increases with higher pH and temperature.
Test at: Daily, especially after heavy feeding or rain.
Quick fix: Stop feeding; water exchange 30–50%; add zeolite (10 g/m³).

⚡ Nitrite (NO₂⁻)

Ideal

<0.1 mg/L

Acceptable

0.1–1.0 mg/L

Danger

>1.0 mg/L

Why it matters: Binds to hemocyanin causing brown gill disease and respiratory failure.
Test at: Daily during new pond establishment; weekly in mature systems.
Quick fix: Add salt (1–2 ppt) to reduce uptake; water exchange; ensure chloride is present.

🧂 Alkalinity

Ideal

100–200

Acceptable

50–100 / >200

Danger

<50 mg/L

Why it matters: Buffers pH against dangerous swings. Low alkalinity = unstable pH.
Test at: Weekly, and after any pH anomalies.
Quick fix: Add sodium bicarbonate (baking soda) at 15–30 g/m³; add agricultural lime.

🪨 Water Hardness

Ideal

100–200

Acceptable

>50 mg/L

Danger

<20 mg/L

Why it matters: Provides calcium and magnesium for exoskeleton formation during molting.
Test at: Weekly, and before stocking.
Quick fix: Add crushed oyster shell, gypsum (CaSO₄), or calcium chloride.

👁️ Turbidity (Secchi Disk)

Ideal

30–50 cm

Acceptable

15–80 cm

Danger

<10 cm

Why it matters: Indicates phytoplankton density. Too clear = low food production. Too murky = oxygen risk at night.
Test at: Daily, mid-morning.
Quick fix: Too clear: add fertilizer. Too murky: reduce fertilizer, add water exchange.

🚨 Emergency Quick Actions

When parameters go wrong, act fast with these proven responses.

🚨 DO Below 4 mg/L — CRITICAL

Turn on ALL aerators immediately
Perform 30–50% water exchange with clean water
Stop feeding to reduce oxygen demand
Check for blocked aerators or pump failures
Monitor continuously until DO returns to 6+ mg/L

🚨 Ammonia Above 1 mg/L — ACT NOW

Stop all feeding immediately
Perform 30–50% water exchange
Apply zeolite at 10–15 g/m³ to bind ammonia
Increase aeration to boost nitrification
Check for dead crayfish or uneaten feed

🚨 pH Crash Below 6.0

Apply agricultural lime immediately (200 kg/ha)
Add sodium bicarbonate (30 g/m³) for fast buffering
Test alkalinity — likely very low
Perform small water exchanges with buffered water
Investigate cause: acid rain, overfeeding, low alkalinity

🚨 Nitrite Above 1.0 mg/L — ACT NOW

Add common salt at 1–2 ppt to block uptake
Perform 20–30% water exchange
Check for adequate chloride in water
Boost aeration to support nitrifying bacteria
Reduce feeding to lower organic load

📋 Daily Monitoring Schedule

🌅 Morning (6–8 AM)

Check: Water temperature, dissolved oxygen, visual inspection of crayfish.
Why: DO is at its lowest point after a night of respiration with no photosynthesis.

☀️ Midday (12–2 PM)

Check: Water temperature, Secchi disk reading, feed consumption.
Why: Peak photosynthesis; good time for water clarity assessment.

🌆 Evening (5–7 PM)

Check: pH level, ammonia (weekly), feed crayfish, inspect shelter condition.
Why: Evening feeding aligns with nocturnal activity; pH typically highest.