Old Tank Syndrome: What It Is and How to Avoid It

Old Tank Syndrome - What It Is and How to Avoid It

Old and new tank syndromes are considered to be one of the most common problems in the aquarium hobby. Because the longer we run our tanks, the higher is the chance that we can get it.

Old tank syndrome refers to an adverse condition characterized by significant changes in an aquarium’s water chemistry. It is common in established aquarium setups and it is facilitated by negligence or poor aquarium husbandry.

So, what is old tank syndrome? What causes it in our tanks? What are the symptoms? How can we avoid it? How to minimize the damage? You will find answers to these and some other questions here. 

Without further ado let’s get started.

What is Old Tank Syndrome?

Old tank syndrome is a slow accumulation of nitrogen and/or minerals that leads to a slow deterioration of water quality.

To put it in simple terms, KH prevents acids from causing large and rapid drops in our pH, and old tank syndrome often affects the carbonate hardness (KH) of the aquarium water.

For that reason, sudden drops in pH can crash the nitrogen cycle and wipe out all the livestock. Our animals and even plants suffer fatal consequences as a result of such changes.

Note: Until recent times, old tank syndrome was only associated with high nitrate and phosphate levels. Nowadays, it is mostly about neglecting the tank.

What Causes Old Tank Syndrome?

Essentially, there is a steady conversion of harmful ammonia into nitrite and nitrite into the less toxic nitrates. And these nitrates are meant to be removed from the aquarium water since it is lethal at increased levels.

In the same vein, there is the issue of rotting food, fish poop, and decaying plant matter, and they get mixed up in the aquarium gravel and contribute to water quality issues.

Without regular tank cleaning, these wastes will continue to accumulate in the aquarium, hence leading to the deterioration of the overall water chemistry/quality.

Therefore, common causes of old tank syndrome consist of:

  • dirty gravel,
  • uneaten food,
  • fish waste,
  • overstocking,
  • dirty filters,
  • inadequate water changes,
  • decaying plant material,
  • dead animal matter.

In addition, it is important to understand that food cannot be 100% transformed throughout the nitrification and denitrification processes in our tanks.

What I mean is that there will be still different minerals and metals in the food left.

These ‘mineral leftovers’ will also build up with time. Nobody knows when (it can be a year or two, maybe more, maybe less) but eventually there will be so many ‘mineral leftovers’ that they will change the balance and crash the tank. This is a fact.

The Danger of the Old Tank Syndrome

Here comes the most important part.

The slow deterioration of water quality may not affect the animals in an obvious way.

As a result, many of our aquarium pets (like fish, frogs, snails, freshwater crabs, crayfish, dwarf shrimp, etc.)  in our tanks may be able to adapt and survive to this changing water environment for some time.

Of course, some may die while others will contract diseases but it will not happen immediately. It means that you will not see signs of stress like:

  • lethargy,
  • erratic swimming,
  • loss of color,
  • lack of appetite,
  • stunted growth or molting problems, etc.

So, we can be lead into a false sense of security. Because everything seems fine more or less, right?

No, it is not!

Newly added animals are at huge risk of dying shortly after the introduction since they may not be able to adjust to the poor water chemistry in their new environment — having come from a place with optimal water conditions.

For instance, the newly added shrimp failing to adjust to the harsh conditions will most likely get shocked, fall sick and die. Old tank syndrome should be prevented to forestall wipe-out of the aquarium inhabitants.

Unfortunately, there are lots of examples when people lost their fish, shrimp, etc. because of that. The scary part is that – they DO NOT realize the cause! Because other animals look OK.

So, they blame poor acclimation, or shipment stress. After that, they buy new animals and those die as well.

Symptoms of Old Tank Syndrome

Besides oxidation of ammonia to nitrite and nitrite into nitrate, the nitrification process equally results in the production of hydrogen ions (H+) and these affect the pH level.

Note: pH is an abbreviation for the potential of hydrogen ions (H+) present in water.

Hydrogen ions are present in the aquarium water as hydronium and when they bond with carbonates or buffers, the pH increases.

Meanwhile, when hydronium is on the rise without carbonates to prompt bonding, it will acidify the aquarium water, causing a significant decline in the pH level and this can drop further to extreme levels lethal to fish.

Moreover, acidic water — with pH below 6.0 will deactivate the nitrifying bacteria, making it unable to breakdown ammonia into nitrite and nitrite into nitrate, and your aquarium inhabitants will suffer severely.

The symptoms of old tank syndrome include:

  • rising nitrate and phosphate level,
  • declining/acidic pH,
  • increased stress levels in fish and shrimp,
  • excessive algae overgrowth.

Avoiding Old Tank Syndrome

  • Regular maintenance and water testing.

This is key to preventing old tank syndrome in mature tanks. This entails testing the aquarium water regularly to be sure that the parameters are within the ideal or recommended levels.

Also, test your water source to be sure that there aren’t many variations between its pH, GH, and KH values and that of your aquarium water. Strict adherence to a good water testing and maintenance schedule will prevent your tank from experiencing the old tank syndrome.

In addition to proper maintenance practices such as gravel vacuuming and regular water changes to reduce nitrates and replace depleted minerals.

There is no replacing good consistent husbandry.

Note: Top-offs do not count! After evaporation, it will leave behind any trace impurities and minerals that were dissolved in it.

  • Food maintenance.

That’s not all, remove uneaten food to prevent them from rotting and ruining the water quality.

In the same vein, get rid of decaying plant material and decaying animal matter.

  • Filter maintenance.

Filter maintenance is an integral part of good aquarium husbandry. So do well to clean the filter alongside the filter media as it often gets accumulated with debris and grimes.

Replace the filter media with new fresh media after a few months or whenever you notice signs of impairment.

You can read more about it in my article “How to Clean an Aquarium Filter”.

  • Stock maintenance.

Another preventive measure is to avoid overstocking as it puts more load on your aquarium’s biological filter due to the increased waste excretion.

  • Using plants

Plants will consume nitrogen in the tank. However, not all plants are equally effective. Fast-growing plants require a lot of nutrients for growth. So, they will be the most effective.

Treating Old Tank Syndrome

If you diagnose old tank syndrome in your fish or shrimp tank, then you need to take immediate action to fix it.

  • Water changes

In fish tanks: You can change a significant volume of the tank water, up to 30-50%. Be careful, DO NOT do extremely big water changes because a sudden reduction in nitrogen concentration can shock them and make them susceptible to infections, so that’s not advisable.

In shrimp tank: Proceed by changing 15-20% of the tank water as it helps decrease the nitrate and phosphate levels. While at it, test the parameters (ammonia, nitrates, pH, and hardness levels) each day to be acquainted with the present status — that will help in determining the next course of action.

  • Adding buffers

For water hardness (KH and GH), you can give it a significant boost by adding buffers.

In cases where pH is rising but ammonia is not falling, avoid changing the water further and wait out until things stabilize.

  • Cleaning

Furthermore, the filter and aquarium gravel should be cleaned regularly to eliminate waste material. Lastly, keep on testing the aquarium water to ensure the parameters return to safe levels.

Is it possible to get the old tank syndrome if you always have 0 ppm nitrate?

Yes, it is. Even though our test kits do a great job, they are still not perfect and cannot register very small numbers. In addition, we usually do not test all water parameters, just a few.

So, with time, the mineral leftovers will build up and start changing the balance in the tank.

Therefore, doing water changes is not enough in the tank where animals produce a lot of waste. General cleaning is also required.

In Conclusion

Old tank syndrome is a slow and silent killer for animals that already live in our tanks. At the same time, it may easily shock and kill most of the newly added animals.

This syndrome is caused by less maintenance than what the tank actually needs.

In most cases, this syndrome affects water hardness which directly correlates with pH.

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