In order to create a healthy and stable environment for your fish, it is important to cycle your aquarium tank. Cycling an aquarium tank means growing enough beneficial bacteria so that the organic waste from fish, food, and plants will be adequately handled.
This process occurs naturally in your tank if you provide ammonia, bacteria, and proper water conditions. When your aquarium is cycled you can introduce fish, knowing that their poop and other organic waste will be handled.
Bacteria convert toxic ammonia from waste to still toxic nitrite (NO2) while another set of bacteria converts nitrate to the better-tolerated nitrate (NO3). This process is called the nitrogen cycle and occurs naturally in ecosystems.
Let’s go into more detail
You start by adding ammonia, either by buying pure ammonia or by putting a dead fish or shrimp in the tank. Note that house-cleaning ammonia products contain scent additives, which contain unwanted chemicals.
If you introduce pure ammonia, aim for 3 ppm (parts per million).
You then introduce the bacteria. You can either buy bacteria products or get bacteria from established tanks by getting a stone, or other tank artifacts. A part of a sponge filter from a cycled tank has tons of bacteria.
Now you wait and monitor every 2 days the ammonia and nitrite levels. When the ammonia levels fall to 1 ppm add half the initial dosage of ammonia to feed the bacteria and allow them to propagate.
You continue to monitor ammonia and nitrite anticipating a nitrite spike after around 10 days. Add some ammonia only if nitrite levels are below 5 ppm.
Your tank is ready when you can add 3 ppm of ammonia and you find that it is fully converted to nitrate after 24 hours with no ammonia or nitrite trace.
It will take about 2 to 3 weeks for the tank to be ready.
Before introducing the fish you lower the nitrate levels by doing a partial water change and you are ready.
How to measure ammonia dosage
If you get pure ammonia with no dosage instructions use this calculator. You can also try one drop for every 2 gallons of water. Wait a bit and test. Repeat until you reach the 3ppm mark.
A note about using dead fish or shrimps for ammonia
This way of adding ammonia needs more patience. Chopping the dead fish or the shrimp into chunks will help accelerate the process. Monitor ammonia levels and remove dead fish if ammonia spikes too high. Fresh dead fish or shellfish with intestines, that have not been frozen contain lots of beneficial bacteria, which is an added bonus.
What is the optimum level of nitrates?
It is a popular belief that fish can tolerate nitrate levels up to 80 ppm. This is a somewhat controversial subject. In the case of betta fish, I opt for safety and advice to aim for levels of 10 ppm. Do a partial water change and test. Repeat if needed.
About water parameters
Chlorine kills bacteria. If you are using tap water use a dechlorinator. Or opt for better water sources as explained here.
You want the Ph in the mid-range of 7.0. This is will work for both bacteria, fish, and plants.
How much water should you change?
Unfortunately, there is no fixed percentage. One tank might need 50% water change while another 80%. Let water testing be your guide. You aim for 10 ppm of nitrates.
Should you use a heater?
Bacteria like warm water. A temperature of 78-85F is optimal. They will survive lower temperatures, but cycling will take longer. Using a heater will help if you are living in colder regions.
Will airstones help cycling?
Yes, they will. Bacteria consume oxygen. Every way that will help with oxygenating the water will help the process. Use an air pump. If you have a filter turn it on.
How about lights? Do I need them to cycle the tank?
Bacteria do not need light. On the other hand, bright lights might enhance the growth of algae. Algae might compete with bacteria for nutrients. Better to turn lights off, although light only becomes a problem if you experience algae overgrowth.
Do you do water changes during cycling?
No, a water change during cycling defies the purpose of building up ammonia to induce bacteria growth. A water change should be reserved for the end of the cycle before you introduce the fish. After the partial change, I advise letting the water rest for 24 hours before introducing the fish.
How do you test the water?
Use an aquarium liquid water test kit. Test strips are more convenient but I find them unreliable.
Do plants help metabolize nitrates?
What does it mean to cycle a tank with live fish?
Instead of ammonia, one can introduce live fish that will produce waste to kick off the cycle. Unfortunately, the first batch of fish will probably die. This is an inhumane way and would advise against it.
By cycling your aquarium tank, you provide an environment that is healthy for your fish. This process occurs naturally if you provide ammonia, bacteria, and proper water conditions. When your aquarium is cycled, you can introduce fish with confidence that organic waste will be handled by beneficial bacteria.
About the author
Hi, I am Alex.
My passion is aquariums. I am especially drawn to betta fish. I love experimenting, learning, researching, and writing about them.
You can find the articles I wrote here