What to Do When Your Aquarium Is Completely Cycled

saltwater aquarium

It's crucial to be patient and move slowly once your new has reached the third and final step of the nitrogen cycling process and completed its mission of constructing the beginning of your tank's biological filter foundation.

The newly produced nitrifying bacteria (nitrobacters) are still infants, and they will require time to mature and reproduce. These bacteria are living organisms that require oxygen and food to exist (ammonia or the bio-load, which is primarily generated by waste from all things living in an aquarium). The more organisms living on the surfaces of everything in the system, the better they are able to absorb the bio-load imposed on the aquarium. When the bio-load "exceeds" the established nitrifying bacteria population, ammonia will begin to surface in the aquarium again, and if the load is really heavy, nitrite will most likely occur as well.

If you introduce new animals or disturb your biological filter too fast after your tank has completed its cycle, you risk developing "new tank syndrome," so take it gently at this stage.

Tidy up the System

It's time to clean up the system and get it ready for some new animals after the ammonia and nitrite levels have gone to zero at the end of the second phase of the nitrogen cycle process.

The term here is "light." Remember that the newly born nitrobacters that have evolved during the last step of the nitrogen cycling process are an important element of the biological filter base in your aquarium. These helpful bacteria dwell on all surfaces in the aquarium and are responsible for keeping your system balanced as it matures and multiplies. You don't want to take them away and diminish their numbers at this point, so here's what you can do.

  • Clean off the inside tank walls.
  • Remove any organic waste that has settled on the bottom of the aquarium by lightly siphon cleaning the "surface," and only the "surface" of the substrate.
  • Remove organic matter that has accumulated inside and around rock formations. This can be done by either squirting water into these areas using a turkey baster, or simpler yet, use a small powerhead. It's a great way to easily dislodge the gunk that gets trapped, releasing it into the water column where it can then be removed through filtration.

Perform a Water Change

A water change can be done in combination with cleaning out the system after the ammonia and nitrite levels have gone to zero. Old water is removed during the light siphon cleaning procedure, and the aquarium is then refilled with new saltwater.

Doing a 20 percent to 25 percent water change at this point is beneficial for the following reasons.

  • It replenishes essential seawater trace elements.
  • It helps to correct and return changes in pH, alkalinity and other important parameters of the water to their ideal settings.
  • It improves the overall quality of the water.

Once the aquarium is cleaned up and refilled, it's time to rinse out or replace any mechanical water filtering materials, such as prefilter flosses, cartridges, sponges or pads.

Now let the system run for a few days to allow the filter(s) to polish up the water. If at this point any prefiltering materials appear to be dirty, clean them up again.

Tip: During the cycling process, no water changes or ammonia-destroying items should be introduced to the water, since this would simply delay and prolong the cycling process.

Add Some New Livestock

Test to determine if the ammonia and nitrite levels are at zero, and the pH is proper, after allowing the system to run for a few days after cleaning it and doing a water change. If any traces of ammonia or nitrite remain, wait until they are gone before adding fresh cattle, and when everything is ready, proceed with caution!

You don't want to put a strain on the system. Otherwise, ammonia levels will certainly rise. Snails, hermit crabs, and other hardy tank janitors, as well as one or two major diatom and macroalgae-eating fish, such as Tangs, Angelfishes, and Blennies, are great additions at this time.

Stabilize the System

After you have added a few new additions to the aquarium, allow the system to run for several weeks to become stable before continuing.

After introducing the first new animals, you should test the water regularly for evidence of ammonia and nitrite. The longer you wait to add anything new to the system, the better, because this allows the beneficial bacteria to grow and reproduce, strengthening the biological filter foundation.

When all looks good, go ahead and add a few more new pieces of livestock as you did before.

Establish a Regular Aquarium Maintenance Routine

The key to keeping an aquarium in prime shape and having a happy fish or reef tank community is to take care of it.

Of course, all aquarists should follow certain fundamental daily processes, but there is no fixed framework for conducting additional weekly, bi-weekly, monthly, or longer in between maintenance duties. Everyone has an opinion and a rationale for what, when, and how frequently every given duty should or may need to be performed, and no two aquariums are set up or managed the same way.

We can provide you some maintenance routine suggestions, but only you can decide what has to be done and when it should be done. As your tank grows, you'll have a better understanding of it, and you'll be able to design a regimen that suits your aquarium's unique maintenance requirements.