Cycling a Turtle Tank the Right Way: Ammonia, Nitrite, Nitrate Made Simple

Cycle your turtle tank the right way with an easy plan that turns ammonia into harmless nitrate using proven steps clear charts and handy widgets for dosing testing and water changes so beginners avoid stalls protect shell health prevent odors and build a stable biofilter that keeps water clear and turtles thriving for longer

Cycle Snapshot
1) Seed

Dechlorinate, add starter bacteria or used media, run filter & aeration.

Cycle Snapshot
2) Feed

Dose ammonia to 2–3 ppm TAN fishless or control feeding if turtle-in.

Cycle Snapshot
3) Read

Test daily track NH / NO₂ / NO₃ until 0/0 in 24h then add turtle.

Codingace Turtle Care

Why Cycling Matters for Turtles

Turtles are high-bioload animals. Even a single juvenile slider can outpace the biological capacity of a fresh filter if you skip the nitrogen cycle. Cycling establishes two key bacterial communities: ammonia-oxidizers that convert ammonia (NH3/NH4+) to nitrite (NO2-), and nitrite-oxidizers that convert nitrite to nitrate (NO3-). A mature biofilter protects shell and skin health, prevents persistent odors, and extends filter service life.

Nitrogen Cycle Diagram Placeholder

Tip Keep the filter running 24/7. Beneficial bacteria live in biomedia, sponges, and on hard surfaces and require oxygenated water flow.

Target Levels & Safe Ranges

ParameterNew Tank TargetMature Tank TargetHard Limit (short term)
Ammonia (NH3/NH4+)0.00 ppm0.00 ppm≤ 0.25 ppm
Nitrite (NO2-)0.00 ppm0.00 ppm≤ 0.25 ppm
Nitrate (NO3-)< 40 ppm10–30 ppm80+ ppm → water change
Cycle Timeline Cheat Sheet
PhaseTypical DaysWhat You SeeAction
Seed0–3Little visible changeDechlorinate, add bacteria, aerate
Ammonia Drop3–14NH3 falls, NO2 risesDose 1–2 ppm daily
Nitrite Drop7–28NO2 falls, NO3 climbsProof test 2.0 ppm
Mature21–420/0 in 24 hLarge WC, add turtle
Proof Test Flow
Proof Test Flowchart Placeholder

Exact Step-by-Step Plan

  1. Day 0: Dechlorinate the tank and filter media. Heat to ~24–26 °C and run the filter plus an airstone for strong oxygenation.
  2. Dose ammonia to reach 2.0–3.0 ppm TAN using the calculator below. Use pure household ammonia without surfactants, dose gradually, and re-test after mixing.
  3. Test daily for ammonia, nitrite, and nitrate. Record results in the Cycle Log to chart progress and get automated stage estimates.
  4. When ammonia hits 0 within 24 h and nitrite spikes, continue dosing to 1.0–2.0 ppm daily.
  5. When nitrite also hits 0 within 24 h (nitrate rises), perform a large water change to bring nitrate under 40 ppm.
  6. Proof test: Dose 2.0 ppm ammonia. If it returns to 0/0 in 24 h, your tank is cycled. Add the turtle and feed lightly for the first week.

Emergency cycling with turtle-in: Control feeding (¼–½ normal), test daily, keep ammonia/nitrite ≤0.25 ppm with partial water changes, and use a quality conditioner as directed. Never rinse biomedia in tap water.

Interactive Widgets

1) Ammonia Dosing Calculator

Calculate how much household ammonia to add to reach a target TAN. Defaults assume density ≈ 0.96 g/mL (5%) and 0.90 g/mL (10%).

Your display volume (exclude sump if separate).
Use 1.0–3.0 ppm for cycling.
Common: 5% or 10%.
Defaults: 5%→0.96, 10%→0.90.

2) Water-Change Percentage Calculator

Lower ammonia or nitrite to a safer level. This uses a simple dilution model.

75 gal ≈ 284 L.

3) Dechlorinator Dosage Helper

Estimate how much conditioner to add based on chlorine/chloramine content and your product strength (mg neutralized per mL). Always follow the label.

If unknown, your water report may list a typical range.
Enter from label; default is generic 10 mg/mL.

4) Cycle Progress Estimator & Log

Track your daily readings. The estimator uses simple heuristics to guess your stage and suggests next actions.

DateNH3NO2NO3TempKH
Stage: n/a ETA: n/a
Next Action: add first reading to begin.

5) Nitrite Spike Helper

High nitrite can stall cycling. Use this helper to plan water changes and optional salt support. Always prioritize partial water changes and aeration.

6) Weekly Maintenance Planner

Set a cadence for testing, water changes, and pad rinses based on volume, turnover, and feeding frequency.

Troubleshooting Stalls

Ammonia never drops
  • Water too cold (raise to 24–26 °C), add aeration.
  • Chlorine/chloramine damage: re-check dechlorination, treat refill water before it contacts biomedia.
  • Overdosed ammonia (>4 ppm): perform partial water change and redose to 2 ppm.
Nitrite stuck high
  • Pause ammonia dosing and increase aeration.
  • Perform 50–70% water change to dilute nitrite.
  • Ensure KH ≥ 3 dKH for bacterial stability.
No nitrate showing
  • Check expiration dates on test kits.
  • Heavily planted tanks may consume nitrate—wait 2–4 days and re-test.
  • Cycle may still be early—continue logging daily.
Biofilter crash after cleaning
  • Never rinse biomedia in tap water; use tank water.
  • Stagger maintenance so not all media is disturbed at once.
  • Re-seed with bottled bacteria or used media, and reduce feeding temporarily.

Frequently Asked Questions

Most tanks complete the cycle within 3–6 weeks under 24–26 °C with steady ammonia dosing and good aeration. Your log will show ammonia and nitrite reaching zero within 24 hours as a sign of maturity.

It’s safer to fishless-cycle. If you must keep the turtle in, reduce feeding, test daily, and use partial water changes to keep ammonia and nitrite ≤0.25 ppm. Consider a conditioner that temporarily binds ammonia.

Not strictly, but quality bottled bacteria or used media can shorten the cycle. Store products properly and dose per label.

Transient odors occur as waste breaks down. Maintain aeration, avoid overfeeding, and perform partial water changes as needed. Odors stabilize once nitrification is complete and maintenance is consistent.

Most nitrifiers perform well near 24–26 °C. Cooler water slows bacterial growth; very warm water can lower dissolved oxygen and stress turtles.

It may reduce free-floating bacteria. If you’re starting from scratch, consider leaving UV off for the first 2–3 weeks, then enable it once biofilm is established.

Glossary

TAN
Total Ammonia Nitrogen. Hobby kits show TAN as “ammonia”.
Biofilm
Sticky bacterial matrix on surfaces that hosts nitrifiers.
KH
Carbonate hardness. Buffers pH and supports stable nitrification.
Proof Test
Dosing 2.0 ppm TAN and verifying it returns to 0/0 in 24 h.

Related Calculators

Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.