Dr Tim's Ammonium Chloride
$Calibrated dosing ammonia for fishless cycling. Drops let you hit exact ppm targets safely — much more controllable than household ammonia.
The fishless cycle is the responsible, no-stress way to establish a working biological filter. You set up the tank, feed it ammonia yourself, and grow the bacteria colony to full strength before any fish enter the system. By the time you add livestock, the tank is ready to handle them without ammonia or nitrite ever climbing into the danger zone. Here's the exact protocol, day by day.
What you need before you start
- Fully assembled tank with filter and heater running (heater set to 78–82°F to speed bacterial growth)
- Pure ammonia source — Dr Tim's Ammonium Chloride is the standard. Avoid janitor ammonia that contains dyes, surfactants, or scents.
- Liquid test kit — the API Freshwater Master Kit covers ammonia, nitrite, nitrate, and pH
- Dechlorinator — Seachem Prime is the network standard
- Optional: bottled bacteria starter (Dr Tim's One & Only, refrigerated)
- Optional and powerful: a handful of established filter media from a friend's cycled tank
API Freshwater Master Test Kit
$$Liquid drops for ammonia, nitrite, nitrate, and pH. Essential — strip tests don't have the accuracy needed for cycling.
Dr Tim's One & Only Live Nitrifying Bacteria
$$Refrigerated live bacteria starter. Used correctly with seeded media, can shave a week or two off a cycle. Skip the unrefrigerated shelf brands.
The protocol
Day 0 — Tank setup
- Fill the tank with dechlorinated tap water. Add Seachem Prime at the bottle's recommended dose for the full tank volume.
- Start the filter and heater. Set heater to 78–82°F — bacteria reproduce faster in warm water.
- Dose ammonia until water tests at 2 ppm. Re-test to confirm.
- Optional: add the full bottle of refrigerated bottled bacteria.
- Optional and faster: if you have seeded media from a friend's cycled tank, drop it into your filter now. This can take days off the cycle.
Days 1–10 — Ammonia processing phase
Test ammonia daily. For the first week, ammonia will sit at 2 ppm or slowly decline. Around day 7–10, you'll see it drop noticeably and nitrite appear. When ammonia falls below 1 ppm, re-dose back to 2 ppm. Don't go above 2 ppm — higher concentrations can stall the cycle.
Days 10–25 — Nitrite processing phase
This is the longest phase. The bacteria that eat nitrite grow more slowly than the ones that eat ammonia, so nitrite typically spikes to 2–5 ppm (sometimes higher) and stays elevated for a week or two before crashing. Continue dosing ammonia to 2 ppm when it drops below 1 ppm. Don't do water changes during this phase — they slow the cycle by removing the nitrite the bacteria are growing on.
Days 20–35 — Cycle completion
Watch for the moment nitrite crashes to 0 ppm. Once both ammonia and nitrite read 0 within 24 hours of dosing 2 ppm of ammonia, your tank is cycled. Test for two consecutive days to confirm, then do a single 50% water change to bring nitrate down before adding fish.
Stocking after cycling
Add fish slowly. 2–3 small fish at a time, then wait 1–2 weeks before the next addition. The bacterial colony will grow to match the new bioload, but only if you give it time. Adding 10 fish at once will spike ammonia for several days even in a freshly-cycled tank.
What can go wrong
| Symptom | Likely cause | Fix |
|---|---|---|
| Ammonia won't drop after 2 weeks | pH too low or temperature too cool | Raise heater to 82°F; check pH. Below 6.5, bacteria struggle. |
| Nitrite stuck high after 4 weeks | Chloramine residue or salt | Heavy Prime dose, 50% water change with dechlorinated water |
| pH crashes during cycling | Low KH buffer in tap water | Add a small amount of baking soda per 10 gallons to bump KH temporarily |
| Cycle completes, then ammonia spikes after adding fish | Added too many fish at once | Daily 25% water changes for a week until ammonia stabilizes |
Speeding it up — what actually works
Three accelerators are genuinely effective; everything else is marketing. In order of impact:
- Seeded media from an established tank. A handful of mature filter sponge, ceramic rings, or even gravel from a cycled tank can drop your cycle to under a week. This is the single biggest accelerator in the hobby.
- Refrigerated bottled bacteria. Dr Tim's One & Only and Tetra SafeStart Plus contain live nitrifying bacteria. Used fresh and refrigerated, they can shave a week or two. Shelf-stable products at room temperature are mostly placebo.
- Warm water. Bacteria reproduce fastest at 78–84°F. Bumping the heater for the cycle period speeds things measurably; drop it back to your target temp once cycled.
What doesn't work: ammonia-detoxifiers as the only treatment, plant-only cycling for serious bioloads, and any product claiming a "24-hour cycle." The wait is real, but accelerators stack.
For the underlying biology of why this works, see our complete nitrogen cycle explainer. For what to actually stock after cycling, see our community fish guide.
FAQs
Can I speed up a fishless cycle?
Yes — seeded filter media from an established tank is the most reliable accelerator (can drop the cycle under a week). Bottled bacteria can shave one to two weeks if refrigerated and fresh. Raising temperature to 82°F also helps.
How much pure ammonia do I add to start a fishless cycle?
Enough to bring water to 2 ppm — test after each addition. Dr Tim's drops are calibrated for easy dosing. Household ammonia varies in concentration and may contain unsafe additives.
Do I need to do water changes during the fishless cycle?
Generally no — water changes slow the cycle by removing the nitrite the bacteria are growing on. Exception: if pH crashes below 6.5 or nitrite goes off the chart, a partial change can rescue the cycle.
What's the difference between fishless and fish-in cycling?
Fishless uses dosed ammonia in an empty tank — slower but harmless to livestock. Fish-in cycles with hardy fish present and requires daily Prime dosing and frequent water changes to keep ammonia below toxic levels. Fishless is always preferred when possible.
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