Fishless Cycle Ammonia Calculator

Dosing schedule

This is Dr. Tim’s recipe 3. It assumes you also add their bottled nitrifying bacteria (One & Only) on day 1. Without bottled bacteria the cycle is slower, so go by your test results, not the calendar.

1. Day 1: add one dose (the amount above).
2. Days 2 to 8: test ammonia, nitrite and pH every day and write the results down.
3. Days 3 and 6: if ammonia and nitrite are both below 5 ppm (as nitrogen), add another dose. If either is above 5 ppm, skip it.
4. If pH drops below 7: change 25 to 30% of the water, taking it from near the top, without disturbing the gravel or filter.
5. Day 8 on: when ammonia and nitrite are both below 0.5 ppm, the tank is cycled. If not, keep testing daily.

Never go above 5 ppm NH3-N or NO2-N during the cycle 2^,3. Dr. Tim’s also recommends not using household ammonia 9.

Once the tank passes, here’s how to stock it, and in what groups.

Formulas

• Effective volume (gal) = tank gallons × (1 − displacement). Liters = gallons × 3.785 5.
• ppm NH3 = ppm NH3-N × 17.03 / 14.01 (× 1.2156) 6.
• mg of nitrogen needed = ppm NH3-N × liters.
• Dr. Tim’s: drops = gallons × 4 × (target ppm ÷ 2). Old bottles: 1 drop per gallon per 2 ppm. 1 drop = 0.05 mL 1^,2.
• Household ammonia: mg NH3 = mg N × 17.03 / 14.01; mL = mg NH3 ÷ (% NH3 × density × 10). Density comes from the ammonia density table, interpolated between rows 4. A label in % ammonium hydroxide is converted with × 17.03 / 35.05 8.
• Ammonium chloride powder: mg NH4Cl = mg N × 53.49 / 14.01, assuming pure NH4Cl 7.