We’ve all been there. The aquarium is all set up, the temperature is right where it needs to be, and at this point we’re DYING to add fish! The question we ask ourselves is “Is the aquarium ready for fish?” or “Do I need to cycle ? for how long? In this article we will take a practical approach to starting up or “Cycling” a saltwater aquarium.

Cycling and Bacteria – A Simple Explanation

Let’s cover the basics…what is a “cycled” aquarium? Simply stated, a cycled aquarium has enough beneficial bacteria living on surfaces in the aquarium/sump/filters to convert ammonia and nitrite to nitrate. We will not go in-depth about bacteria types or the specifics of the cycle process – there are plenty of articles and videos online for that. For the purposes of this article, all we want to focus on is how to have enough bacteria to remove toxic ammonia and end up with nitrates that are safe for fish unless in very high concentration.

The “Old” Method

Back in the early 2000s, my research led me to cycling with uncured live rock and some damsels. The purpose of cycling this way was to create waste from die-off on the rock and from food and waste from the damsel fish. In turn, this waste will feed the beneficial bacteria and help it populate and increase. The damsel fish are notorious for being able to cope with ammonia and thus used often in cycling. There are a few problems with cycling this way. First, pests and unwanted “hitchhikers” like crabs and worms would often make it into our tanks. Second, different strains of algae that populate the rock were introduced to our aquariums. Third, putting the damsels through such a process is not very friendly to the animal. Fourth, collection of live rock from our reefs is far from environmentally friendly – there are ground harvested reef rocks now as well as man-made reef rocks which can look spectacular and have no impact on our oceans.

The “New” Method

These days, there are better ways to cycle a tank more responsibly and with less problems. We find it easy to use ground harvested rock that is typically found in Florida. The rocks are mined from an ancient reef that was covered by the Florida landmass many years ago. By doing so, fish and animal communities are unaffected. The rocks also look great, are porous and come in different shapes and sizes. Another source of good looking reef rock is the man-made rocks offered by a few companies. These rocks are made with the same components and minerals as real reef rocks and even come with purple coralline-like colors. Using either the ground-harvested rock or man-made rock is a great way for us to help ocean conservation and to allow us to have a better startup for our aquarium. Also, using wet live-sand is great to use because it comes with beneficial bacteria seeded in the sand. The live sand is less cloudy than dry sand and requires no rinsing. To seed the aquarium with bacteria we like to use a cycling liquid available from several manufacturers which we will cover in the next section.

Using Cycling Liquids

Several years ago when I first discovered beneficial bacteria liquids for aquariums, I was skeptical and unconvinced it was helpful. After experimenting with it in our own aquariums and now using it for many years, I can say that they work and work well. The liquids are added once the temperature is in the mid-seventies or higher and it is recommended to remove any mechanical filtration and UV sterilization. There are a few brands out there but we’ve used Dr. Tim’s One and Only with great success. You can read more about and purchase it at https://store.drtimsaquatics.com/.

Cycling With Fish

Now that we have bacteria liquids, live sand, and rocks with no die-off we can safely start an aquarium with some fish without causing them harm or exposing them to high levels of ammonia. We usually pick a group of fish that are inexpensive and hardy. We would typically add more fish every 2-4 weeks to allow the bacteria population to catch up with the newly added waste of newly added fish.

Cycling Without Fish

There are ways to cycle an aquarium and get beneficial bacteria levels high without adding fish. What needs to be done is pretty simple – we need to mimic the waste created by a group of fish without the fish :) One way is to take a piece of shrimp from the supermarket and put it in the aquarium for it to decay and create waste. Another way is to simply add fish food to the tank every day. Some folks even use ammonia chloride and add it into the aquarium to get the tank to grow beneficial bacteria. It’s worth noting that the bacteria levels in the aquarium will balance to the amount of waste that exists. So if you were to have a huge amount of beneficial bacteria in an aquarium but very little fish, eventually the bacteria population would diminish down to be just enough for the existing fish and created waste.

Using Established Media

Another great way to start a tank is by using established media from another established aquarium. We keep a bunch of different media types in our systems that we can transfer into a new aquarium. We are often asked to stock up customers’ aquariums quickly, so adding established media with beneficial bacteria already populating it is a great way to get started and avoid any types of delays.


Starting up (or cycling) a new saltwater aquarium is not difficult. These days the aquarium hobby and industry is mature and have developed many ways to have an easy and successful startup. We hope that we have simplified the cycling process for you and that you will have a successful startup of your aquarium!