Cycling an aquarium is a concept we've covered before. Twice this year, in fact, with a video release by our staff and a blog post shortly thereafter by Dr. Tim himself, Dr. Timothy A. Hovanec.

Maybe you've heard about the importance of cycling an aquarium before today. Perhaps this is your first time reading about it.

The reason you must cycle an aquarium before adding fish and coral is because your tank needs time to grow beneficial bacteria. This bacteria will help process waste (uneaten food, fish poop, etc.) to make your aquarium a safe and habitable environment for animals. This process of waste being broken down is often referred to as The Aquarium Nitrogen Cycle. Creating the right conditions in your tank for this cycle to occur is usually referred to a biological filtration.

We definitely encourage you to check out the aforementioned content before we dive into this Recipe for Success, just so you're familiar with the various concepts, terminology, and products mentioned herein.


*A 2 oz. bottle of ammonium chloride is enough to cycle aquariums up to 250 gallons


Set up your new aquarium, filter, and heater per the manufacturer's instructions.

DrTim's Aquatics One and Only Live Nitrifying Bacteria need a place to live so, for best results, your tank needs to have gravel or crushed coral on the bottom of the tank.

After you initially set up your tank, the water may be cloudy and cold. It is therefore preferable to let the system run overnight before adding One and Only just to make sure everything is OK. If you have a protein skimmer, UV sterilizer, and/or ozonizer, it is best to set them up and test the connections BEFORE adding One and Only. If you are going to use a filter sock, you can install it now to remove particles from the water.

Another thing you should do before adding One and Only to your aquarium is to dose your tank with the appropriate amount of DrTim's Aquatics First Defense to remove any chlorine and/or chloramines in your water. These elements and compounds can harm the live bacteria in DrTim's One and Only.

After dosing First Defense, wait 30 minutes before adding One and Only. DO NOT add any ammonia removing solutions. You should also remove your filter sock and turn off your protein skimmer, UV sterilizer, and/or ozonizer. These pieces of equipment should remain off for a full 48 hours after adding One and Only Live Nitrifying Bacteria to your aquarium.

To add One and Only, shake the bottle well for several seconds. Then pour the ENTIRE BOTTLE into your aquarium. You can also add One and Only to your sump or filter. Your aquarium water may become cloudy, but don't worry: it will clear up in a short time.

Next, add 4 drops (and 4 drops only*) of DrTim's Aquatics Ammonium Chloride per gallon of aquarium water. This is "Day 1" in the chart below. We recommend that you DO NOT use household ammonia.

Wait 24 hours—now we are on "Day 2" of the chart below. Measure the ammonia, nitrite, and pH levels of your aquarium water. Record these measurements by writing them into the chart below.

On "Day 3," add another 4 drops of ammonia per gallon of aquarium water**. Measure and record your water quality for 2 more days (days 4 and 5 on the chart below).

On "Day 6," add another 4 drops of ammonium chloride per gallon of aquarium water**. Measure and record your water quality for 2 more days (days 7 and 8 on the chart below). At this point, in most cases the ammonia and nitrite will be zero or below 0.5.

Fishless Cycle


Your aquarium is now cycled.

You may begin adding fish to your aquarium so you can really starting enjoying your tank! Continue following the schedule on the chart below for a successful start. At the conclusion of week 2, perform a 25% water change.

*Precautions: Do not add ammonia until you get a reading of 2 ppm NH?-N. Do not add ammonia every day. If the pH drops below 7, perform a 25-30% water change and take water from near the top of the water column. Do not disturb the substrate or remove the filter pad. Do not manipulate pH during the cycling period. The higher the pH (up to 8.5), the better!

** If the ammonia or nitrite values are over 5 ppm NH?-N, skip the next addition of ammonia drops.

***Check out this article for more information on how to fishless cycle your aquarium.

DrTims Fishless Cycle

Download a PDF version of this recipe