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4 Reasons Your Oscar Fish May Have Died!

Although oscar fish, sometimes known as velvet cichlids are considered to be a hardy fish, they are not the easiest fish to care for and they can be prone to a number of problems that may result in a premature death of the fish.

With the recent spike in the number of people adding oscars to their aquariums recently, there seems to have been a spike in these problems with many people reaching out to ask why their oscar fish died.

There are generally three main causes of premature death in oscar fish with the most common cause being adding the oscar to an uncycled tank.

The second most common is usually stress and anxiety with there being multiple ways the stress and anxiety levels of your oscars can be spiked and cause problems.

The third most common cause of premature death in oscar fish is disease but this is often much easier to notice in the fish than the other two causes.

We are going to be going over the three most common causes that your pet oscar fish may have died in more detail below to try and help prevent the same problems from happening to any other oscar fish that you may have.

One common problem that is easy to avoid is that people put their oscar in a tank that is simply too small for them and although rare, this can also result in a premature death of the fish so we will also touch on that more at the end of the article too.

Being Added To An Uncycled Tank!

The most common reason that an oscar fish may have died is due to being added to an uncycled tank where the ammonia and/or nitrate levels can spike resulting in a premature death of the fish.

Depending on the exact setup of the tank, the increase in bioload of a large oscar fish can be enough to cause ammonia and nitrate to spike too if tank maintenance is not carried out on a regular basis.

Even experienced fish keepers who have been keeping fish for decades can have problems with this, especially if they are used to keeping smaller fish as the increase in bioload really can take you by surprise.

You really should be cycling your tank if possible and although a “good” bacteria colony is not essential, is it probably the quickest, easiest, and cheapest method to cycle your tank with ease.

Although oscars are a relatively cheap fish, you should still do your best to prep your tank for them to avoid any potential problems like this that may result in a premature death.

If your oscar did die due to having problems with the ammonia and nitrate levels in the tank then this could end up causing problems for other fish in the aquarium too so keep an eye out for any other sickly looking fish.

“Astronotus ocellatus – Oscar Fish” by Daniella Vereeken is licensed under . To view a copy of this license, visit undefined?ref=openverse&atype=rich

A Spike In Stress And Anxiety!

Although oscar fish are considered a hardy species, they can be susceptible to stress and anxiety spikes that may result in your oscar dying prematurely.

The two main causes of this is the oscar being added to a new tank or an oscar already in your tank having new tank mates added to it that nip it or chase it.

This is a less common reason that your oscar fish may have died than ammonia and nitrate issues but it is still common enough to feature in our list.

The aggressive, fearless reputation that oscars can have in some fish keeping circles leads people to think that the fish is not susceptible to stress or anxiety spikes but this is not correct and it can sometimes result in serious problems or even death in the fish.

Other sources of stress and anxiety spikes in oscar fish that are commonly overlooked is toxic shock and temperature shock too with both being common in tanks maintained by people new to fish keeping.

Thankfully though, both are easy to avoid if you monitor your water levels on a regular basis and keep an eye on the temperature levels of your aquarium water.

Suffering From Disease!

Just like all other fish, oscars are susceptible to various types of diseases that can cause the fish to die.

The majority of these diseases do have a number of early warning signs that tend to be obvious to see in most fish suffering from them so you can usually research the symptoms your oscar is displaying to quickly find a suitable treatment.

Unfortunately, there are so many diseases that can take hold of your oscar that it is not practical to go into them all in this article but a quick Google search will often be enough for you to identify the problem as well as the best treatment to help get your oscar back to full health.

Many of these diseases can also be contagious so you may have to try to quarantine the affected oscar or look to treat all of the fish in your primary aquarium.

With some people keeping multiple oscars in the same tank, this is definitely something to keep an eye out for is one of your oscars has died as the disease could be taking hold of your other fish too.

Some of these issues can be traced back to our first point of ammonia and nitrate levels being too high in the tank you put your oscar in stressing the importance of maintaining suitable water parameters.

The Tank Is Too Small!

A very common problem that may result in an oscar fish dying is if it is kept in a tank that is just too small for it.

A single adult oscar usually requires a tank size of 55-75 gallons with two adult oscars needing a tank that is 100 gallons minimum.

Anything smaller than this can cause stress and anxiety to spike in the fish as well as aggression levels potentially resulting in the death of the fish.

With oscars being such a popular option right now, many people brand new to fish keeping at getting baby oscars and adding them to small tanks not realizing that they can grow to around ten inches in length.

As the fish grows, it can quickly get too big for the tank that it is in and if you have multiple oscars in the same small tank then aggression between them will quickly break out.

We know that the larger tanks that adult oscars require are expensive but upgrading your tanks to a larger size is often unavoidable in many situations like this or you risk the fish having problems as it grows.

You can often find large tanks at a discounted rate on sites such as eBay with some local classified sites often giving large tanks away for free provided you collect the tank too.


That brings our article going over the three most common reasons your oscar fish may have died to an end. We also touched on the tank size issue that is common with oscars too although it is less likely that that will result in the death of your pet oscar fish. All of these issues are avoidable but some do need you to plan ahead before you even get your oscar to make sure that your tank size and water parameters are optimal for the species.