(NTS) New Tank Syndrome

Just set up a new aquarium?

Now you will discover that your new aquarium will become subject to a condition called NTS as soon as the first fish is introduced.

NTS can be overcome eventually by being patient and taking things slowly!

What is NTS?

NTS is the lack of beneficial nitrifying bacteria in your aquarium and biological filter, therefore creating a breakdown in the nitrogen cycle. (Insufficient sewage works).

This can then have a knock on effect:

1) Breakdown of the nitrogen cycle.

2) Increased concentration of toxins in the aquarium.

3) Stress and physical damage to delicate membranes, i.e. gills.

4) Lowered immune system.

5) Fish open to disease and infection or even sudden death.

What are beneficial nitrifying bacteria?

These are bacteria that convert dangerous fish waste into less harmful by-products, which plants can then use as a type of fertilizer, this is called ‘nitrification’. (Sufficient sewage works)

There are two types of these nitrifying bacteria:

1) Nitrosomonas- converts ammonia into nitrite.

2) Nitrobacter- converts nitrite into nitrate.

Both of these types of nitrifying bacteria are needed in the nitrogen cycle.

AMMONIA –     Comes from fish waste / uneaten rotting food / rotting dead leaves / unnoticed dead fish. Ammonia is dangerous to the fish’s health, but only lasts for a short while in the aquarium before nitrosomonas bacteria converts the ammonia into nitrites.

NITRITES –      Very dangerous to the fish, plants, and even the nitrifying bacteria themselves at high levels. The nitrites will last for quite some time (creating a very stressful environment for the fish), but eventually the nitrobacter bacteria multiply enough to cope with converting the nitrites into nitrates.

Nitrites can cause your aquarium water to turn cloudy or foggy and the fish may be gasping for oxygen.

Increase aeration where possible.

NITRATES –    Live plants can help control the nitrates. Nitrates are only dangerous at very high concentrations and can affect the fish and plants only at these levels.

Carrying out 25% weekly water changes will help reduce the nitrates to a safe level in your aquarium. It will also help to reduce any disease outbreaks by diluting any pathogens.

Where can I get some beneficial nitrifying bacteria?

These bacteria are everywhere, including in the mature water that your fish comes with from the shop. So as long as you take things slowly, then the nitrogen cycle will set itself up.

You can also buy these bacteria suspensions, available in bottles from your local aquatic shop, but this is just a booster and not a short cut.

Ready to buy your first fish?

Add one teaspoon (5 grams) of aquarium or cooking salt to every gallon (4.55 Litres) of aquarium water to reduce the effects of nitrite on the fish, this will also act as a mild antiseptic and help increase the protective slime coating on your fish, so keep to this concentration when water changing.

Remember a little salt is good, more is not always better.

Buy only one fish, possibly two for larger aquariums.

This fish must be non – shoaling and hardy (ask at your local aquatic shop) to cope with stress and strains of starting up the nitrogen cycle for you!

Place the tied bag containing the fish into your aquarium and let it float for 10 mins to allow the fish to become acclimatized to the temperature of your aquarium.

Now add some of your aquarium water into the bag to let the fish become acclimatized to your water chemistry, i.e. pH / hardness etc… every 5 minutes three or four times.

Now release your fish by gently tipping the bag and contents into your aquarium. Keep an eye on the fish for any unusual behaviour so that any problems can be detected early.

Feed only once every three days and gradually build up to once per day as much as they will eat in 30 seconds.

Water change 30% – 50% every other day to dilute nitrite levels until the filter is ‘mature’.

Keep any toxins in check by testing the water, which can be done for you at your local aquatic shop where control methods can be discussed. Alternatively you can buy your own test kit. Testing frequently will tell you when you can add further fish into your aquarium.

Once your aquarium is ‘mature’ (this is when the bacteria have multiplied enough to cope with the waste produced by the fish – usually 4 – 5 weeks) you will no longer have to worry about dangerous toxins.

Alternatively you could use live aquatic plants to do the hard work for you instead of fish which is safer and nicer to the fish when they eventually go in.

The method for this is (as above) but without having to feed and only performing minimal water changes every few days depending on the nitrite levels.


When cleaning the filter media (usually a type of foam), wash it in a jug or bucket of aquarium water so that you do not kill your nitrifying bacteria like you would if it was washed with tap water containing chlorine.


Fish tank / lid  / stand / light unit [ ]       Gravel / ornaments / backing paper [ ]  Power filter [ ]

Air pump / line / stone [ ]          Heater (tropical only – 24 degrees celcius) [ ]  Thermometer [ ]

Dechlorinator [ ]           Fish food [ ]     (when tank is ready)… Plants [ ]           Fish [ ]