How To Cycle A Salt Water Aquarium

Now that you have filled your beautifully aquascaped tank with salt water mixed to the perfect salinity and allowed any sand that was disturbed to settle it is time to turn on the heater, fire up the return pump and….. Definitely not add fish or corals yet.  While your beautiful new tank may look ready to welcome its first inhabitants there is one final step to be completed.. Cycling.


Basically cycling a tank establishes a biofilter that allows the tank to support fish, corals and other invertebrates.  In the past, this meant waiting many weeks or months for the biofilter to slowly establish.  Some reefers even used hardy fish such as damsel fish to cycle a tank, although this has very much fallen out of popularity due to the unnecessary distress it causes the fish.

Thankfully, here at Reef Casa we have a product that can dramatically cut down the amount of time it takes to cycle your tank without using live animals.  However, even with our additives and live bacteria you can expect tank cycling to take a minimum of a few weeks.  Remember, in reefing patience is key!

So what exactly does “tank cycling” mean?  Essentially the cycle that is being referred to is the nitrogen cycle.  Over the course of the nitrogen cycle the Reef Casa Foundation dry rock that you used to create your aquascape will become “live rock” and will be colonized by millions of bacteria that will help to detoxify fish waste and other organic material in your tank.


Step 1: Add ammonia source

The first step of the nitrogen cycle requires a food source for the new live bacteria to eat, survive and reproduce. This is food source is ammonia and you can use Reef Casa Life Bottle 1: Ammonium Chloride to kick start the cycle.  If there are fish in the tank at this point the ammonia is harmful and it will begin to burn their gills and reduce the oxygen supply in the water, which is why it is important never to cycle a tank with live fish.


Step 2: Introduce a denitrifying bacteria


In order to reduce ammonia to zero so we can add fish we introduce a denitrifying bacteria. You can use Reef Casa life Bottle 2: Live Bacteria to accomplish this

These living bacteria will consume ammonia and kick start the cycle process. As the ammonia is consumed, another byproduct is released called nitrite.  Eventually the levels of ammonia and ammonia consuming bacteria will reach an equilibrium and the ammonia levels will level off and then drop to zero.

While nitrite is less toxic than ammonia, it is still dangerous to fish and other invertebrates.  As the levels of nitrite begin to rise a new type of bacteria, Nitrobacter, will begin to consume it.  Similarly to ammonia levels, the levels of nitrite will rise and then plateau and fall as the nitrite eating bacteria colonize the rockwork, sandbed etc.   The final by-product of this reaction are nitrates, which are far less toxic than ammonia or nitrites and can be controlled with water changes.

So how do you know when the nitrogen cycle has been completed?  Here at Reef Casa we suggest testing for ammonia every few days until levels begin to rise and then fall followed by testing for nitrites in a similar manner.  Once ammonia and nitrite levels have risen and fallen to zero you should then check for nitrates to ensure that some are present in the tank.

Reef Casa Life Cycling products will cycle a new aquarium safely in roughly 2 weeks. Be weary of other brans or companies that claim to cycle tanks in only a few days or even worse hours. Nothing good in this hobby happens fast and patience is key.


Although we can not see the bacteria, by using test kits we know that they are there. Nitrates can only be present if the bacteria and doing their job, consuming ammonia and producing it


Once ammonia levels are 0, nitrite is at 0 and nitrates are present, the cycle is complete.

At this point you can add one or two fish to the tank.  It is important to resist the urge to overstock  because adding more fish will produce more ammonia and your tank will have to find a new equilibrium.  Over the course of several weeks you can then begin to slowly stock the tank, being sure to monitor levels of ammonia in particular.

Once your tank is fully cycled and stocked the bacteria that colonized the rockwork and sand should keep ammonia and nitrite levels at zero and nitrates can be controlled through water changes or other chemical filtration media.  While it can be tempting to rush the cycling process it is important to be patient and ensure that you are testing the water regularly and ensure that the cycle is complete before adding any livestock.  If you have any questions about cycling please reach out to us.  Happy reefing and congratulations on your fully aquascaped and cycled tank that is now ready to become a beautiful addition to your home!