Quick Guide: Fishless Cycling with Live Bacteria

Setting up a reef tank for success starts with cycling. If you’re looking for a no-fish method to establish a healthy nitrogen cycle, this simplified guide will walk you through the fishless cycling process in clear, manageable steps.

For a deeper dive into the science behind cycling, we recommend checking out comprehensive guides from experts. But for now, here’s your quick-start recipe to get cycling—whether or not you choose to use bottled nitrifying bacteria.

• Liquid ammonia solution
• Ammonia and nitrite test kits (a pH test kit is also recommended) We use the API Saltwater Master Test Kit
• Live nitrifying bacteria (We used  DrTim’s One & Only)
• Patience and consistency

Day 1:

Add entire 2 oz bottle of One and Only Live Bacteria to the tank and turn off UV sterilizers, protein skimmers, and remove filter socks for at least 48 hours to let the bacteria settle. We added the whole 2 oz bottle at once. 

Next, Wait 1 hour and add ammonia to your tank to reach approximately 2 ppm of ammonia-nitrogen (NH₃-N). If you’re using DrTim’s Ammonium Chloride (post-November 2016 version), dose 4 drops per gallon. Don’t stress about hitting 2 ppm exactly—it’s more important not to overdose. We did 80 drops which is 4 milliliters. 

Day 2:
Test your water for ammonia and nitrite levels. 

Day 3:
If both ammonia and nitrite are under 1 ppm, dose again with 4 drops per gallon of ammonia.

Days 4 & 5:
Continue monitoring ammonia and nitrite.

Day 6:
If both parameters remain below 1 ppm, add ammonia again—4 drops per gallon.

⚠️ Note: If using bottled bacteria, ammonia test kits may not register a full 2 ppm. Don’t keep adding ammonia to “force” a higher reading. Just dose and move on.

Days 7 & 8:
Keep testing daily. Once you see both ammonia and nitrite drop below 0.5 ppm, you’re nearly there.

From this point on, test every day.

When both ammonia and nitrite are consistently below 0.2 ppm, dose the tank one more time with 2 ppm ammonia.

Once the tank can process that ammonia within 24 hours (ammonia and nitrite both under 0.2 ppm the next day), your cycle is complete!

Congratulations! Your tank is cycled.

Now you can perform a water change and start introducing your first fish.

• Avoid high concentrations: Keep ammonia and nitrite below 5 ppm at all times. Higher levels can stall the cycle.
• Watch pH levels: If your pH drops below 7.0, do a partial water change to bring it back up.
• Skip ammonia removers: These products can interfere with the cycle and make things take longer.
• No need to feed daily: Bacteria don’t need daily ammonia—overfeeding can cause excess nitrite buildup.
• Bare-bottom tanks take longer: If you're cycling a tank without substrate, consider adding inert objects like glass marbles or ceramic media to give bacteria more surface area to grow.