Old tank syndrome is a problem that can plague even the most experienced fish keeper. This problem is rooted in poor water conditions and can lead to many negative conditions for all kinds of fish.

That is why understanding as much as you can about old tank syndrome, how to prevent it, and how to treat aquariums that already have it is vital knowledge for any sensible aquarist. In this article, our experts share what they know about it and how you can prevent or resolve this aquarium problem.

What Is Old Tank Syndrome?

Simply put, old tank syndrome refers to the condition of an aquarium with poor water chemistry or neglected water parameters. This problem can occur in both new and established aquariums, though it is more likely to happen in the latter.

Aquariums with old tank syndrome have high levels of bacteria, nitrates, and ammonia. This tank problem can lead to multiple fish deaths and the degradation of aquatic fauna. In less severe cases, old tank syndrome might not lead to the death of a fish, but it will likely be the root cause of widespread disease among the aquarium inhabitants.

What Causes Old Tank Syndrome?

Old tank syndrome is one of the many aquarium problems caused by a fish keeper’s neglect or failure to maintain consistent and high-quality water conditions in any inhabited aquarium. Below is a list of some of the most common factors that lead to the occurrence of old tank syndrome.

– The Fish Keeper Did Not Perform Regular Aquarium Water Changes

Fish keepers who fail to perform regular water changes in their aquariums put their fish at great risk of suffering from different illnesses. This failure to cycle tank water on a regular basis is also the leading cause of old tank syndrome.

Cycling or changing water in fish tank is an easy enough task to accomplish. Depending on your tank’s population, size, and water parameters, you might have to change or cycle your aquarium water by 10 to 15 percent per week.

– The Tank Has Built up a High Amount of Waste Matter

Aquariums that are not properly maintained are likely to have a high amount of waste matter. This waste comes from uneaten food, dead plants, and fish feces. In general, fish excrete feces through their gills and skin, while some species of fish excrete feces through pores found near their tail fins.

This fecal matter, along with the other waste that naturally accumulates in the fish’s environment, results in a dirty fish tank and an increased chance of death and disease among the aquarium inhabitants.

– You Have Too Many Fish in the Same Aquarium

This is one of the most overlooked causes of old tank syndrome. Having too many fish in one aquarium leads to a faster buildup of waste. As we just learned in the previous paragraph, a high amount of waste matter in the tank’s water will inevitably result in more nitrates, phosphates, and harmful bacteria that weaken the immune system of all fish in the aquarium.

How Can I Tell If My Aquarium Has Old Tank Syndrome?

There are some signs and symptoms of old tank syndrome that you can easily identify if you are already familiar with them. This will help you stay proactive in keeping your aquarium in peak condition for the prevention of old tank syndrome and other water problems.

Read on to find out more about the signs you should watch out for if you suspect your aquarium has old tank syndrome or if you just want to prevent this problem from occurring in the first place.

– The Nitrate and Phosphate Levels in Your Tank Have Increased Significantly

One of the easiest ways to check if your aquarium has old tank syndrome, or is well on the way to developing the aforementioned condition, is by checking on the tank’s nitrate and phosphate levels. An increase in the level of nitrate in aquarium water is one of the signs that your tank is suffering from rapid waste buildup.

You can buy nitrate and phosphate test kits at your local fish stores. These kits usually come in two types: paper strips or colored dyes. You will only need a sample of the water from your aquarium and a test kit of your choice to determine the current nitrate and phosphate level of your tank.

– Your Aquarium Water Registers a Low PH Level or Has a Strongly Acidic Quality

While many freshwater fish can survive and even thrive in slightly acidic water, the majority of fish species will develop illnesses if they are forced to live in highly acidic conditions. Aquariums with highly acidic water also have high amounts of ammonia, among other harmful substances. Too much ammonia is toxic to fish and can lead to poisoning or eventual death.

– New Fish Die Shortly After Being Introduced to Your Aquarium

Often, when newly introduced fish die in the aquarium after only a few days, aquarists are quick to blame it on that fish’s health. However, this is not always the case.

When new fish die more often than survive in an established tank, it is most likely due to fluctuating or inconducive water conditions. The new fish are shocked at the acidity of the tank water or the amount of nitrates and phosphates present in the aquascape.

This shock can be enough to damage the fish’s body permanently or else lead to death if the fish in question is particularly young or not from a hardy species.

Once you see these signs and symptoms manifest in your home tank, it would be wise to perform tests and water changes to check if your aquarium already has old tank syndrome. In addition, below is a table of figures that you should watch out for if you suspect your aquarium might be developing old tank syndrome.

Ammonia Level 1.5 mg/L and above
Nitrite Level 0 mg/L and above
Nitrate Level 40 mg/L and above
pH Level 6.0 and below

What Are the Best Preventive Measures Against Old Tank Syndrome?

Now that you know the causes of old tank syndrome, you should also learn about the actions you can take to prevent such a problem from occurring in your home aquarium. Here are some of our experts’ proven methods for keeping an aquarium’s water conditions consistent and conducive for healthy, happy, and long-lived fish.

1. Schedule Regular Water Testing Sessions

Making a habit out of monitoring or testing your aquarium’s water parameters is always a good idea, especially if you are still a novice fish keeper with a new tank setup. You should aim to test water conditions at least once every three days. You can then decrease the frequency of your water testing sessions once you have achieved ideal tank water conditions consistently for at least one month.

2.  Perform Small Water Changes on a Regular Basis

Aside from regular water testing sessions, you should also know how to perform small water changes to your aquarium. You can opt to change the water of your aquarium every week or every two weeks, depending on the fish population and tank size.

Here is an example of a water changing schedule that you can use as a template for your own tank maintenance activities. Keep in mind that the figures below are just estimates.

Water Change Frequency Amount of Water to Cycle or Change
Once every seven days 10-15 percent
Once every fourteen days 20-25 percent

3. Add Live Plants to Your Aquarium for Added Filtration and Nitrate Control

Including live plants in your aquascape can help provide more oxygen for your fish while increasing your tank’s water quality.

Planted tanks are more efficient than bare or substrate-only tanks at maintaining favorable ammonia and nitrite levels.

This is because live plants aid in converting ammonia, and they also need nitrites to thrive. Live plants will actively feed on the ammonia and nitrites in your tank, thus making it easier for you to maintain ideal water conditions for your fish.

Keep in mind that this is only true for planted tanks that are neither overstocked nor overcrowded. You need to strike a balance between the fish population and the number or volume of live plants you keep together, especially when it comes to maintaining a closed system like an aquarium.

What Are Some of the Best Aquarium Plants for Old Tank Syndrome Prevention?

Now that you know live plants are a great help when it comes to keeping high amounts of nitrates, phosphates, and even ammonia at bay, you might be wondering about exactly which plants to include in your aquarium. Here are our experts’ top picks for the best aquarium plants that will aid in the prevention of old tank syndrome.

– Java Fern

The common Java Fern is an easily accessible and low-maintenance plant that even beginners can grow in their aquariums.

This freshwater plant does not grow at a rapid pace, but it will help in effectively converting carbon dioxide to oxygen in your tank. This means that your fish will not only have an additional form of shelter or place to rest, but they will also benefit from an increase in consumable oxygen and cleaner water.

– Anubias Barteri

The Anubias Barteri is yet another common freshwater plant that is slow-growing and easy to maintain. Given enough time, the Anubias Barteri can prove instrumental in reducing the amount of nitrates in your aquarium. It also has no need for a substrate and can be grown by attaching its rhizomes to wood and rock debris.

– Hornwort

The humble Hornwort is an excellent nitrate regulator due mainly to its rapid growth and hardy nature. Novice aquarists will find that Hornwort is easy to keep and propagate because the plant can thrive in substrates, attached to wood or rocks, or even when it is left to float on the water surface.

While these live plants will certainly help in regulating the amount of harmful substances in your tank water, it is important to note that you still need to perform water changes and tests on a regular basis.

What Is the Best Treatment for Aquariums With Old Tank Syndrome?

Most experienced fish keepers will tell you that slow and steady water changes on a daily basis will help you fix old tank syndrome.

However, aquarium problems such as old tank syndrome can vary in severity depending on the tank in question. That said, some aquariums might need a more drastic treatment than simple water cycling.

Here are some of the more serious actions that our resident aquarists have taken to fix aquariums afflicted with old tank syndrome. We have also included tips on what to do if you ever have to handle an aquarium that undoubtedly has old tank syndrome.

1. First, Assess the State of Your Aquarium

Before applying any treatments or drastic repair methods, you would be wise to first take a long and hard look at your aquarium.

Do the fish seem sick or listless? Do you notice an overgrowth of algal blooms in the tank? Can you see a lot of waste matter floating in the water?

You can ask yourself these questions to determine the severity of the state of your aquarium and then plan on what to do from there. Alternatively, you can also ask for the opinion of a trusted and experienced fish keeper if you are unsure of how to proceed.

2. Consider Executing Increased Water Changes More Frequently Than – Usual

If the level of nitrates in your tank has skyrocketed or your fish are becoming more sickly, then you might need to consider performing water changes on a more frequent basis. You can also increase the amount of water that you change or cycle out.

For example, instead of changing 10 to 15% of your tank water weekly, you might want to shift to a more aggressive strategy by changing 25% of the tank water in one go. You can then repeat this large water change after a day or two.

Such frequent and large volume water changes are necessary for aquariums that are at the brink of having their entire fish population wiped out due to high amounts of nitrates, ammonia, and algae.

The 25% volume water change won’t shock your fish as much as if you make the mistake of changing half or all of the water in an aquarium at once. In addition, giving the fish a chance to recover from the water change for 24 to 48 hours will help in preventing fish death due to shock.

3. Learn How to Reboot Old Fish Tanks Properly

For treating extreme cases of old tank syndrome, restarting a fish tank is usually the best way to go. An old fish tank that has been severely neglected and has few to absolutely no more surviving fish will not recover if you only implement minimal water changes and cleaning procedures. These cases require research, preparation, time, and renewed commitment from the fish keeper.

While restarting a fish tank might seem to be a daunting task, it can actually be broken down into these simple steps:

– Store the Existing Setup Materials and Plants Properly

If you want to reuse the substrate, decor, and live plants from an old fish tank, you need to rinse them gently with water and store them in large containers. This will prevent overcrowding and damaging the existing setup materials; this will also help you avoid stressing out your live plants.

– Use Cleaning Chemicals To Prepare Your Substrate and Decor

Choose high-quality bleach and algicides to use on your substrate, wood debris, and decor. Apply these substances after you manually comb through the substrate, removing any fine dust or clumped waste. You can also use your hands to remove any rotting wood debris or broken parts from your decor.

– Allow the Tank To Cycle for a Few Days Before You Introduce Live Plants and Fish

Let the aquarium filter run for at least 24 to 48 hours before introducing the substrate and wood debris. Then, allow the tank to cycle again for another 24 to 48 hours before planting your aquarium fauna. Allow the plants sole dominion over your tank for 48 to 72 hours before introducing new fish in small batches.

Wrapping Up: Old Tank Syndrome

We learned a lot about old tank syndrome, how to diagnose and treat it, and most importantly: how to prevent it. Below is a recap of the most important points we covered in this article.

  • Old tank syndrome is mainly because of a fish keeper’s neglect.
  • An increase in nitrates, nitrites, phosphates, and ammonia usually indicates that your aquarium has old tank syndrome.
  • Including live plants in your tank setup can help prevent old tank syndrome.
  • Performing regular water tests and changes can go a long way in keeping your tank clean and healthy.
  • It is vital that you know how to restart old fish tanks that suffered from old tank syndrome.

With these points in mind, you should have an easier time preventing old tank syndrome. Apply what you’ve learned from this article to ensure the health and happiness of all of your aquarium inhabitants.

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