The most common mistakes made during aquarium cycling

The most common mistakes made during aquarium cycling

Aquarium cycling is the most important process for any marine aquarium. This issue is quite puzzling for many aquarists. In this article, I will describe the most common mistakes that aquarists make at the beginning, and which later negatively affect the maturation of the aquarium.

Table of Contents

Rock-related errors

Aquarists who have not taken the time to study the subject properly and learn, for example, how a rock should be arranged in an aquarium, make a lot of mistakes with its proper preparation.

The most common rock-related mistakes:

  • the rock is leaning against the back of the aquarium, causing dirt to collect underneath it
  • there is too much rock and it sticks to the sides of the aquarium (it should be arranged so that water can circulate freely)
  • the rock has not been glued together and is falling apart
  • too low a rock quality was chosen and the aquarium takes a long time to cycle
  • the rock was bought from an unverified source and with it we bought various plagues
  • the live rock was immersed in RO water which killed all life from the rock
  • rearranging the rock in the aquarium – changing the position of the rock starts the maturation process anew
  • removing the rock from the tank, for example, to clean it of algae – removing the rock from the tank will cause the cycle to start over again

Constantly changing salinity

Young aquarists, who are not yet able to reproducibly test water, make erroneous measurements and change the salinity. The problem most often results from the fact that they calibrate the refractometer incorrectly and are not aware that the salinity at this stage cannot change. They manipulate the water by changing the salinity.

The second mistake that young aquarists make is that instead of supplementing the evaporated RO water, they add brine. Evaporated water is always topped up with RO water!

Too many bacteria

Some aquarists think the more the better. They add too much bacteria, and then we have a bacterial bloom. To get rid of it, we have to weaken the entire biology. To remove the bacterial bloom, we use a UV lamp that reduces the amount of bacteria. We remember that at the maturation level, the point is for the bacteria to guide our aquarium through the process of nitrification. Killing the bacteria is not recommended.

At this point, it can also be added that it’s worth using good quality bacteria that accelerate maturation. There are bacteria on the market that have almost no effect at all, what prolongs the maturation process.

Too fast water changes

Aquarists start doing water changes while the tank is still maturing – we shouldn’t be doing that. The first water change can only be done when the aquarium is mature. I recommend doing a 5% water change as your first water change. After changing the water, we observe how our tank behaves.

Adding fish and corals too soon

It’s better to wait with the animals until the tank is mature and ready. Adding animals too quickly can destabilize the biology, which extends the maturation process.


Patience and gaining knowledge in this hobby are the key. The more we read and the more patiently we wait, the better for the aquarium.

About the author

Picture of Marek Protasewicz

Marek Protasewicz

Reefkeeping has been my passion for over 10 years now. I love learning. The hobby has taught me many valuable lessons, patience being the best example. Combining work and passion is my path. I run Crazy Coral, a marine aquarium shop, for a number of years. Building this business from the scratch I learnt from my own mistakes at a heavy cost.
Later I managed a project aimed at development of methods for quick growth of Corals in non-natural conditions. The project was carried out by Get Sales, Poland. Presently, I am responsible for distribution strategy at Reef Factory, of which I am a co-founder. The company produces smart devices for marine aquaristics. The last projects I have been involved in are Social Reef and ReefPedia.

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