By BETH ANN BATES
What is new tank syndrome? It’s
the undesirable outcome of a
natural, biological cycle that occurs
in new fish tanks when they are
poorly planned. It’s also one of the
reasons many new fish-keepers
abandon the hobby in
discouragement. New tank
syndrome will kill your fish, so you
absolutely want to avoid it. To do
that you must have a basic
understanding of the nitrogen cycle
(also referred to as cycling a new
tank). There is enough biological and chemical science in this process to overwhelm the
non-scientist. Yet understanding it is critical to your success as a freshwater hobbyist. So
my goal for this article is to give you the important stuff in plain language, with as little
scientific jargon as possible. The good news is that you really don’t need a profound
scientific mind to understand enough to keep a healthy tank.
Fish tanks differ from natural aquatic environments in that tanks are closed systems.
What goes in, stays in. There is no rainfall or tide to push pollutants out of your tank. This
puts fish-keepers at a disadvantage. Waste products that are naturally occurring in your
tank include uneaten food, fish urine and feces, and decaying plants. How do we deal
with these wastes?
One way hobbyists minimize wastes in their tanks is by partial water changes. On a
regular basis, the hobbyist removes part of the tank’s water and replaces it with fresh,
clean water. Many people also vacuum the gravel, cleaning up uneaten food and fish
feces (called mulm) in the process. This greatly improves the water quality.
Another way that hobbyists eliminate waste is by water filtration. All tanks, other than the
tiniest fish bowls, are equipped with a water filter. This will be a machine, run on
electricity, that pulls water from the tank into a filter that cleans it, then the clean water is
circulated back into the tank. These electric filters run continually, 24 hours a day. This is
one of the reasons that a power outage can spell trouble for your tanks.
The filter media is usually a dense sponge or tread-like product that catches dirty
particles in the water and traps them. The filter media can be inside or outside of the
tank. I use a box filter. It hangs off the back of the top of the tank, with an intake tube that
hooks from the tank out into the box. The box holds the sponge. Many people also like
filters that have the sponge (sometimes big and round) inside the tank. Either way, the
sponge serves the same purpose. This is what is called mechanical filtration. The water
is mechanically filtered through the sponge or other media, trapping any solid particles of
dirt so they do not return to the water. These sponges need to be cleaned occasionally,
but there are important do’s and don’t for this, explained in a bit.
Another element can be what’s referred to as chemical filtration. This usually involves the
use of activated carbon or charcoal to clean the water. My filter, for example, contains both
a sponge and a packet of carbon. The carbon absorbs pollutants in the water. These
carbon filters eventually reach their limit of capacity and should be replaced. As with
almost everything in this hobby, you will find disagreement among hobbyists as to the
need for carbon and/or how often it must be replaced. The brand that I use recommends
monthly replacement, so I try to stick to that schedule.
The third element is what’s called biological filtration. This is where the nitrogen cycle
comes into play. Biological filtration, (or biofiltration) is a critical aspect of keeping your
tank healthy. The filter media and other parts of your tank, such as the gravel, develop
colonies of bacteria. Before you run screaming for the bleach—wait! Not all bacteria is
bad; the kind that grows in your tank’s filter is good and healthy. In fact, it’s critical to the
wellbeing of your fish. New tank syndrome is actually caused by a LACK of this healthy
bacteria.
Okay, here’s where all the science stuff comes in. The biological process known as the
nitrogen cycle is initiated by the presence of ammonia in your tank. This ammonia is
created by the fish waste, both liquid and solid, as well as the breaking down of uneaten
food and/or dead plants in your tank. This is somewhat ironic. Since the nitrogen cycle
can be so dangerous to fish, we might like to cycle a new tank before adding fish. But the
cycle can not start without them! (Well, truthfully, there are some tricks of the trade in that
regard, more on that later.)
The nitrogen cycle can be broken down into three parts. The first part is the build-up of
ammonia in your tank caused by the presence of fish waste. Ammonia is very toxic to
fish, so here’s your first danger. However, the ammonia starts the cycle because bacteria
develops in response to the ammonia. This bacteria basically eats the ammonia (okay—
that’s the non-scientist way to describe it). This is wonderful! Now your fish are rid of that
nasty danger. But wait, there is a by-product of this first part of the cycle: nitrites.
With the development of nitrites, part two begins. The danger here is that nitrites are only
somewhat less dangerous to your fish than bully number 1, Ammonia. So here we go
again. Not to worry, more bacteria to the rescue! Now other bacteria will develop to
convert the nitrites into nitrates. I warned you it was confusing. Despite the similarity in
the terms, they are two different things, with the last one being the least dangerous for
your fish. Once you have zero ammonia, nitrites and nitrates, then you’re in great shape.
Your tank has successfully developed the healthy bacteria it needs. This whole process
can take weeks to a month, even longer, but it is too important and dangerous to rush it.
The best way to avoid new tank syndrome is to plan your new tank with self-control. All
hobbyists, especially new ones, want lots of fish. When you set up a new tank, it’s hard to
resist the urge to stock it heavily. A good local store that specializes in aquarium fish will
advise you on how many fish you can put in your new tank. This is one of the reasons
why I recommend that new hobbyists bypass the superstores and find a good local
specialty store, if possible. Near my home in New Jersey, I am fortunate to have a
number of good stores. The first one I was lucky enough to find has wonderful
employees who guided me in the right direction (see www.absolutelyfish.com).
Overstocking your new aquarium is the fast route to new tank syndrome. The best plan is
to start off a new tank with a small number of hardy fish. Later, when the cycle is
complete, you may add additional fish. In other words, you really should not put all the
fish you want into a new tank at the same time. It’s not easy to exercise that much self-
control, but your fish will thank you for it.
So, what are you doing while this Nitrogen cycle is happening? Great question! The
answer is, you must be monitoring the cycle by testing your water repeatedly. How do you
do this? You’ll need to purchase a water testing kit, which any fish or pet store should
have. There are a couple of options. I use the style of kit that comes with small test tubes.
You fill the tubes with water from your aquarium, then you add a specified number of
drops from different bottles that come with the kit. The water changes color and you
check the resulting color against a chart. Another type of testing kit uses strips of paper
that you dip into the tank. The paper changes color to indicate the amount of substance in
the tank.
Whichever type you get, be sure it includes testing for ammonia, nitrites and nitrates.
Your testing results during the cycle will follow the stages discussed above, with the rise
of ammonia occurring first. Your test kit should give you guidelines for the results,
indicating what colored reactions are high enough to be dangerous. If the ammonia is
too high you need to do a partial water change to bring it down.
Reacting to the cycle is yet another area of debate within the hobby. Some people might
tell you that you should never change the water during the initial Nitrogen cycle. I must
disagree. Yes, it is true that doing water changes during this time will lengthen the time it
takes to finish the cycle, but without them, you are likely to lose fish. This is where the self-
control you exercised earlier pays off. If you did not stock the tank heavily, your ammonia
will hopefully not rise to the point that your fish suffer or you are forced to change the
water. It also helps to exercise self-control in the feeding of your fish. Overfeeding
contributes to the build-up of ammonia in the tank, so feed lightly.
When the ammonia level in the tank starts to fall, you will be on the lookout for nitrites,
and you’ll follow the same procedures for water changes if the levels become
dangerously high. During the first two stages of the cycle, you probably should test the
water daily or close to it.
Another option is the new ammonia and nitrite monitors that attach to the inside of the
tank with suction cups. These may be less precise but are very convenient. When both
ammonia and nitrates are at zero, the cycle is complete. Nitrates may be present, but
they are only harmful at very high levels. Your partial water changes will address them.
You should continue to test the water on a regular basis.
To keep that healthy bacteria in your tank, do not clean the gravel or filter media with tap
water. The chlorine in tap water will likely kill the beneficial bacteria. You can clean the
sponge while you do a partial water change. Before you dump the bucket of dirty water,
just dunk the sponge in it and squeeze, rinsing it in the bucket.
Do expert hobbyists really go through this every time they set up a tank? The answer is
no. When you are ready to set up your second, third or fourth tank, there is a trick to speed
up this process. If you use filter media and/or gravel from an established, healthy
aquarium, it can jump start the cycle for your new tank. This is how hobbyists with
multiple tanks do it. They may even keep “extra” filters running in their tanks just for this
use. If you browse the web, you will also find a lot of reading about “fish-less” cycling.
This method gets the nitrogen cycle stated by adding pure ammonia to the new tank,
without fish. This is an interesting idea, but I have yet to try it.
Setting up a new tank can be a challenge and a joy. With some planning and monitoring
of your aquarium, you can be successful. Happy fish-keeping!
First published July 2007 in The Animal Companion
What is new tank syndrome? It’s
the undesirable outcome of a
natural, biological cycle that occurs
in new fish tanks when they are
poorly planned. It’s also one of the
reasons many new fish-keepers
abandon the hobby in
discouragement. New tank
syndrome will kill your fish, so you
absolutely want to avoid it. To do
that you must have a basic
understanding of the nitrogen cycle
(also referred to as cycling a new
tank). There is enough biological and chemical science in this process to overwhelm the
non-scientist. Yet understanding it is critical to your success as a freshwater hobbyist. So
my goal for this article is to give you the important stuff in plain language, with as little
scientific jargon as possible. The good news is that you really don’t need a profound
scientific mind to understand enough to keep a healthy tank.
Fish tanks differ from natural aquatic environments in that tanks are closed systems.
What goes in, stays in. There is no rainfall or tide to push pollutants out of your tank. This
puts fish-keepers at a disadvantage. Waste products that are naturally occurring in your
tank include uneaten food, fish urine and feces, and decaying plants. How do we deal
with these wastes?
One way hobbyists minimize wastes in their tanks is by partial water changes. On a
regular basis, the hobbyist removes part of the tank’s water and replaces it with fresh,
clean water. Many people also vacuum the gravel, cleaning up uneaten food and fish
feces (called mulm) in the process. This greatly improves the water quality.
Another way that hobbyists eliminate waste is by water filtration. All tanks, other than the
tiniest fish bowls, are equipped with a water filter. This will be a machine, run on
electricity, that pulls water from the tank into a filter that cleans it, then the clean water is
circulated back into the tank. These electric filters run continually, 24 hours a day. This is
one of the reasons that a power outage can spell trouble for your tanks.
The filter media is usually a dense sponge or tread-like product that catches dirty
particles in the water and traps them. The filter media can be inside or outside of the
tank. I use a box filter. It hangs off the back of the top of the tank, with an intake tube that
hooks from the tank out into the box. The box holds the sponge. Many people also like
filters that have the sponge (sometimes big and round) inside the tank. Either way, the
sponge serves the same purpose. This is what is called mechanical filtration. The water
is mechanically filtered through the sponge or other media, trapping any solid particles of
dirt so they do not return to the water. These sponges need to be cleaned occasionally,
but there are important do’s and don’t for this, explained in a bit.
Another element can be what’s referred to as chemical filtration. This usually involves the
use of activated carbon or charcoal to clean the water. My filter, for example, contains both
a sponge and a packet of carbon. The carbon absorbs pollutants in the water. These
carbon filters eventually reach their limit of capacity and should be replaced. As with
almost everything in this hobby, you will find disagreement among hobbyists as to the
need for carbon and/or how often it must be replaced. The brand that I use recommends
monthly replacement, so I try to stick to that schedule.
The third element is what’s called biological filtration. This is where the nitrogen cycle
comes into play. Biological filtration, (or biofiltration) is a critical aspect of keeping your
tank healthy. The filter media and other parts of your tank, such as the gravel, develop
colonies of bacteria. Before you run screaming for the bleach—wait! Not all bacteria is
bad; the kind that grows in your tank’s filter is good and healthy. In fact, it’s critical to the
wellbeing of your fish. New tank syndrome is actually caused by a LACK of this healthy
bacteria.
Okay, here’s where all the science stuff comes in. The biological process known as the
nitrogen cycle is initiated by the presence of ammonia in your tank. This ammonia is
created by the fish waste, both liquid and solid, as well as the breaking down of uneaten
food and/or dead plants in your tank. This is somewhat ironic. Since the nitrogen cycle
can be so dangerous to fish, we might like to cycle a new tank before adding fish. But the
cycle can not start without them! (Well, truthfully, there are some tricks of the trade in that
regard, more on that later.)
The nitrogen cycle can be broken down into three parts. The first part is the build-up of
ammonia in your tank caused by the presence of fish waste. Ammonia is very toxic to
fish, so here’s your first danger. However, the ammonia starts the cycle because bacteria
develops in response to the ammonia. This bacteria basically eats the ammonia (okay—
that’s the non-scientist way to describe it). This is wonderful! Now your fish are rid of that
nasty danger. But wait, there is a by-product of this first part of the cycle: nitrites.
With the development of nitrites, part two begins. The danger here is that nitrites are only
somewhat less dangerous to your fish than bully number 1, Ammonia. So here we go
again. Not to worry, more bacteria to the rescue! Now other bacteria will develop to
convert the nitrites into nitrates. I warned you it was confusing. Despite the similarity in
the terms, they are two different things, with the last one being the least dangerous for
your fish. Once you have zero ammonia, nitrites and nitrates, then you’re in great shape.
Your tank has successfully developed the healthy bacteria it needs. This whole process
can take weeks to a month, even longer, but it is too important and dangerous to rush it.
The best way to avoid new tank syndrome is to plan your new tank with self-control. All
hobbyists, especially new ones, want lots of fish. When you set up a new tank, it’s hard to
resist the urge to stock it heavily. A good local store that specializes in aquarium fish will
advise you on how many fish you can put in your new tank. This is one of the reasons
why I recommend that new hobbyists bypass the superstores and find a good local
specialty store, if possible. Near my home in New Jersey, I am fortunate to have a
number of good stores. The first one I was lucky enough to find has wonderful
employees who guided me in the right direction (see www.absolutelyfish.com).
Overstocking your new aquarium is the fast route to new tank syndrome. The best plan is
to start off a new tank with a small number of hardy fish. Later, when the cycle is
complete, you may add additional fish. In other words, you really should not put all the
fish you want into a new tank at the same time. It’s not easy to exercise that much self-
control, but your fish will thank you for it.
So, what are you doing while this Nitrogen cycle is happening? Great question! The
answer is, you must be monitoring the cycle by testing your water repeatedly. How do you
do this? You’ll need to purchase a water testing kit, which any fish or pet store should
have. There are a couple of options. I use the style of kit that comes with small test tubes.
You fill the tubes with water from your aquarium, then you add a specified number of
drops from different bottles that come with the kit. The water changes color and you
check the resulting color against a chart. Another type of testing kit uses strips of paper
that you dip into the tank. The paper changes color to indicate the amount of substance in
the tank.
Whichever type you get, be sure it includes testing for ammonia, nitrites and nitrates.
Your testing results during the cycle will follow the stages discussed above, with the rise
of ammonia occurring first. Your test kit should give you guidelines for the results,
indicating what colored reactions are high enough to be dangerous. If the ammonia is
too high you need to do a partial water change to bring it down.
Reacting to the cycle is yet another area of debate within the hobby. Some people might
tell you that you should never change the water during the initial Nitrogen cycle. I must
disagree. Yes, it is true that doing water changes during this time will lengthen the time it
takes to finish the cycle, but without them, you are likely to lose fish. This is where the self-
control you exercised earlier pays off. If you did not stock the tank heavily, your ammonia
will hopefully not rise to the point that your fish suffer or you are forced to change the
water. It also helps to exercise self-control in the feeding of your fish. Overfeeding
contributes to the build-up of ammonia in the tank, so feed lightly.
When the ammonia level in the tank starts to fall, you will be on the lookout for nitrites,
and you’ll follow the same procedures for water changes if the levels become
dangerously high. During the first two stages of the cycle, you probably should test the
water daily or close to it.
Another option is the new ammonia and nitrite monitors that attach to the inside of the
tank with suction cups. These may be less precise but are very convenient. When both
ammonia and nitrates are at zero, the cycle is complete. Nitrates may be present, but
they are only harmful at very high levels. Your partial water changes will address them.
You should continue to test the water on a regular basis.
To keep that healthy bacteria in your tank, do not clean the gravel or filter media with tap
water. The chlorine in tap water will likely kill the beneficial bacteria. You can clean the
sponge while you do a partial water change. Before you dump the bucket of dirty water,
just dunk the sponge in it and squeeze, rinsing it in the bucket.
Do expert hobbyists really go through this every time they set up a tank? The answer is
no. When you are ready to set up your second, third or fourth tank, there is a trick to speed
up this process. If you use filter media and/or gravel from an established, healthy
aquarium, it can jump start the cycle for your new tank. This is how hobbyists with
multiple tanks do it. They may even keep “extra” filters running in their tanks just for this
use. If you browse the web, you will also find a lot of reading about “fish-less” cycling.
This method gets the nitrogen cycle stated by adding pure ammonia to the new tank,
without fish. This is an interesting idea, but I have yet to try it.
Setting up a new tank can be a challenge and a joy. With some planning and monitoring
of your aquarium, you can be successful. Happy fish-keeping!
First published July 2007 in The Animal Companion
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