Introduction

Water quality is essential to get right if you want healthy attractive fish. In fact, it’s often said that keeping fish is more about keeping water than fish. If your water quality is good then your fish will live longer, be more attractive and your hobby will be much more rewarding.

This article explains how to get your fish tank ready for adding fish. You’ll learn some basics about water chemistry and how fish affect the water they inhabit.

Background

Fish, as part of their biological processes, secrete ammonia from their gills and in urine. In the wild this would be diluted by the environment but in a tank this ammonia builds up quickly to levels that will harm the fish. Ammonia in the water can cause breathing difficulties and burn the fish’s skin so obviously this needs to be prevented.

Luckily nature is on your side and provides a way of removing the ammonia. This is known as the Nitrogen Cycle.

The Nitrogen Cycle

The nitrogen cycle might sound like too much science but it’s actually very simple. It’s a three stage process where ‘friendly’ bacteria convert the harmful ammonia to much less harmful nitrate. The diagram below shows how this takes place.

As can be seen there are two types of bacteria that are required for the nitrogen cycle. In simple terms the bacteria consume one compound and emit another.

A New Tank

A newly set up tank will not contain enough of the beneficial bacteria required for the Nitrogen Cycle. Bacteria once given a source of ammonia will start to multiply and colonise the filter and substrate. However these bacteria are slow growing and will need time to multiply to the point of being able to remove enough ammonia for fish to be added to the new tank.

The Solution – Fishless Cycling

As mentioned at the beginning of this article you are going to learn how to prepare your water for fish. This involves getting the nitrogen cycle running by adding a source of ammonia into the tank. There are two methods for this, either adding ammonia from a bottle or dropping small amounts of fish food into the tank as explained below. If you have access to fully cycled media from another tank, squeezing it out in your tank, or adding it to your filter will help start the bacterial colonies you need. Be patient when cycling a tank as it takes 4-6 weeks or even longer to fully cycle a new tank. Remember to treat the water in the tank with water conditioner to remove chlorine or chloramine otherwise bacteria won't grow.

Fishless Cycling – Ammonia method

For this you’re going to need a bottle of household ammonia from the supermarket or chemist, a syringe, a calculator and a test kit for testing ammonia, nitrite and nitrate. (Test kits are an essential part of fishkeeping. It’s the only way you can be sure what’s going on in your tank.)

Household ammonia is typically 10% ammonia, the quantities used in the calculator are based on this. Commonly added amounts to the tank are between 2ppm and 5ppm (parts per million). We recommend 3ppm as a good level so all following instructions are based around using 3ppm.

1) First you need to know how many litres of water are in your tank. This is easy – measure the height, width and length in centimetres and multiply those figures together and then divide by 1000 (or use the calculator on the right). For example a tank measuring 100cm by 50cm by 30cm would hold 150 litres. If you have a lot of substrate and décor in your tank you need to take 10-20% off your calculated figure to allow for this.

2) Use the ammonia calculator at the bottom of the page to work out the amount of ammonia in millilitres (ml) to introduce and add it to the tank.

3) The following day use the ammonia test kit to measure the ammonia in the tank.If it’s below 3ppm (parts per million) use the ammonia calculator below to calculate how much ammonia to add to bring the level back to 3ppm. It may take several days before you see a significant drop.

4) Repeat step 3 every day. This process is to start the cycle off (the initial bacterial growth) and keep the bacteria alive by feeding them ammonia at the correct concentrations in the tank water.

5) After about a week you can start to test for nitrite in the water. Ammonia is converted to Nitrite in the first part of the cycle so when you can detect it, it means the cycle has started.

6) Continue testing for ammonia every day. Whenever it drops below 3ppm add enough ammonia to bring the level back up to 3ppm using the calculator to obtain the correct dose. Also test for nitrite every other day. You should see nitrite rise and then start falling after a few weeks.

7) Start testing for Nitrate after a few weeks. Nitrate is the last part of the process where the bacteria convert the nitrite to nitrate. When the test kit starts showing a fall in the nitrites you should see a rise in the nitrates.

The graph below shows how you should expect the levels of ammonia, nitrite and nitrate to rise and fall over time. The graph shows the test results you would see before adding the daily ammonia.

Fishless Cycling – Fish food method

For this method you will need a tub of fish food and a test kit for measuring ammonia, nitrite and nitrate.This method uses decaying food to provide a source of ammonia that the cycle requires to start.

1) To start, drop a few flakes of fish food into the tank.

2) Leave it for a few days and then test for ammonia.

3) If there’s no reading or the reading is below 3ppm (Parts Per Million) drop a couple more flakes in.

4) Keep testing every other day and add a couple more flakes if the reading is below 3ppm

5) After about a week you can start to test for Nitrite in the water. Ammonia is converted to Nitrite in the first step of the cycle. If you can detect nitrite in the water then the cycle has start.

6) Continue testing for ammonia and nitrite every other day and dropping a flake or two when ammonia drops below 3ppm. After a few weeks the nitrite level should start to drop and if you now start testing for Nitrate you’ll see Nitrate levels rise as the last part of the cycling process converts the nitrite to nitrate.

The graph below shows how you should expect the levels of ammonia, nitrite and nitrate to rise and fall over time.

Fishless Cycling – Ammonia and Fish food combined

If you’ve read the two methods above you may be wondering which is the best method to cycle your tank… Well combining the two methods is actually possible and is the most recommended method. This means you get the more accurate control of using an ammonia source with the additional biological processes that using fish food creates. Combining the two methods will give you a tank to add your fish to that’s more mature and stable.

The graph below shows how you should expect the levels of ammonia, nitrite and nitrate to rise and fall over time. The graph shows the test results you would see before adding the daily ammonia.

Adding Fish

When ammonia and nitrite readings have returned to zero the cycle has completed. If your nitrate reading is above 40 you will need to do some water changes to bring this down. Test your tap water for nitrate first, it may be too high to use to dilute the nitrate in the tank.

The bacteria will need a constant supply of ammonia to keep the cycle going so if you have a cycled tank and aren’t adding fish just yet you need to keep the bacteria alive by continuously adding ammonia or food. Don’t add ammonia at the same time as fish, it’s one or the other and only when the ammonia reading is zero.

Conclusion

This article explained the three stage biological process that converts harmful ammonia to nitrite and then nitrate, commonly known as the nitrogen cycle. If you have any questions or problems with your tank cycling please post in the forums and someone will be able to advise.



Ammonia Calculator



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