Marine Aquarium Cycle

  • Cycling your marine aquarium.

    One of the hardest and longest things a marine aquarium hobbyist will encounter is the cycle of a new aquarium. The excitement and anticipation of starting a new tank is often met with disappointment when finding out you now have to wait 4 to 6 weeks for your new tank to cycle. In this article I will highlight the common processes involved with cycling a new aquarium.

    To start off you have your tank, you add salt water, substrate and live rock. You will also have your heaters, pumps and any other equipment plugged in and running, once all of this is done you now have to sit back and look at a relatively empty tank for a month or so. This is, however, one of the most important aspects of starting a tank because if you rush this process you may end up killing fish and corals and ultimately give up.

    Patience is key in setting up a marine aquarium, we all hate it but we have to do it.

    Here are two graphs which explain how the cycle works and the different elements involved. Please note that the time-lines are just a guide as each tank will cycle differently, but you can count on a rough period of 4 to 6 weeks. You will know your tank has cycled once your ammonia and nitrite levels have spiked and they both read 0 on your test kits.



    Here is an example of how I set up my nano tank.

    The basic tank with lights and in the black filter box is the heater and a circulation pump.

    Here the tank is filled with RO (Reverse Osmosis) water and salt is then added, you can see the salt laying on the bottom of the tank. It is vital that you use RO water to start the tank and also for top-ups as tap water is not suitable and can lead to huge algae problems later on. There is also a circulation pump added which aids in the salt being dissolved. You can also see the tank is not filled up to the top, this allows for the water level to rise when the sand and rocks are added.

    At this point you need to take at least 24 hours to allow the salt to dissolve, you also need to bring your tank up to temperature (about 25 to 27 Celsius). Measure your salinity, (ideally with a refractometer). Your salinity needs to be about 1.025 to 1.026. If it is too high then add some RO water, if it is too low then add some more salt and allow it to dissolve.

    Once the salt has dissolved and the tank is at the right temperature you can then add your substrate. This needs to be very fine sand (sugar grain size or smaller). You can use various shop bought sands like coral sand, aragonite and so on, or you can use sand collected from the sea or a real cheap way to go is to use playsand, very cheap but needs to be washed lots and lots of times. In this tank I used a mixture of caribsea aragamax aragonite and playsand. Your substrate needs to be about 2 to 3 cm's deep to allow for worms and other creatures to populate the sand, this also provides food for the many creatures you will have in your tank. Once the sand is in, your tank will more than likely look very milky, leave it overnight to settle, once the water is clear you can then add your liverock. I rushed it a bit and put rock in straight away, this was not one of my brightest ideas (I have many of those :p) as the dust from the sand settled onto the rock and I had to clean it all off.

    You get different types of live rock, cured and uncured and from various locations around the world where it is harvested from, Kenya, Fiji, Indonesia etc.

    Here is my milky tank shortly after adding substrate and rock.


    A few hours later it is starting to clear up.

    A few more hours later and it was looking lovely :p by the morning it should hopefully be crystal clear. Now this is where the hard part comes in, waiting for the tank to cycle, the long wait, periodic testing of ammonia and nitrite, waiting for the toxic levels to disappear. Hang in there, you'll get through it.

    After a couple of weeks you will more than likely notice some brown algae forming on the rocks, sand and glass. This is called diatom algae and is quite normal for a new tank and can occur in tanks well up to a year old. Grin and bear it, it does go away after a while.

    A couple of weeks further in and you may start getting the dreaded green hair algae creeping in, this is also normal in some tanks, wait for it to get quite long and then pull it out, you may have to do this for a couple of weeks but it will eventually go away. You can reduce your lighting hours to only 2 or 3 hours a day to help stunt the growth of this algae, but you will win the battle. :)

    So there it is in a nutshell, now I know there are many variations of cycling a tank and various other methods such as the zeovit method which allows you to cycle a tank in something like 7 or 14 days, you can try this method but it is a specialised method and needs to be followed to the tee, you also need special equipment and additives to use this method.

    One thing I would recommend using, although not essential, is Seachem Stability or Prodibio BioDigest or Bioptim, these add beneficial bacteria to your aquarium and can help establish the biofilter, I have used both of these with no ill effects. There are also many new products entering the market such as Microbelift and Brightwell Microbacter7 but I have not used these products so cannot comment on them, but they do have some very good reviews. Research all products carefully before using them.

    Before you add any of these or any other products to your tank, ask for advice on the forum, there is a huge amount of knowledge and experience on the forums and the guys are only too happy to share their experiences and advice with you. what? Tank cycled? Yes? Cool....

    Now you can start thinking about adding livestock, add a couple of snails, hermit crabs if you want and then start stocking with fish and corals, but SLOWLY. Add a fish or two then wait a week or two before adding any more livestock, this allows the bacteria and your biofiltration to adjust to the added bioload in the tank. Don't ever stock a tank too fast.

    Have fun and enjoy your marine aquarium. Please feel free to ask any questions or add anything I may have missed.