Aluminum in a Fish Tank – Is It Safe for Fish Tanks? Is It Toxic to My Fish?

Setting up an aquarium or fish tank can be a time-consuming and at times expensive process, so the last thing you want is to add your fish and find that they’re not surviving the conditions of your tank after all of your efforts.

Aluminum is the most abundant metal on earth, so it’s natural to turn to it as a resource to include in your aquarium – but it’s also incredibly toxic to fish and something you want to avoid in your fish tank.

Continue reading this article if you’re considering including aluminum in your fish tank, and ask yourself if it is safe for fish tanks, and will it be toxic to your fish?

Why is Aluminum unsafe in Fish Tanks?

A vast majority of metals will react and oxidize when exposed to water, making them toxic to aquatic life and definitely not a feature you want in your aquarium. Essentially, a chemical reaction between the metal and the oxygen in its surrounding environment creates oxide on the metal’s surface – this is the component that is dangerous to fish.

Aluminum in particular has a high affinity for oxygen, which means that it almost acts as a magnet for oxygen particles, which leads to it oxidizing quickly compared to other metals. Because of this attraction, you don’t need to have aluminum features in your aquarium for long before they start to wreak havoc on the health of your tank.

The solubility of aluminum actually increases as the pH of the environment surrounding it decreases, and it has been found that a pH of 5.2-5.8 encourages high toxicity in Aluminum oxide – most aquatic tanks maintain a neutral pH ranging between 6.8 and 7.6.

What happens if I add Aluminum to my Fish Tank?

So, we’ve explored the chemical process that oxidizes aluminum – but why exactly is this oxide toxic to your fish? 

It has been found that aluminum particles infiltrate the gills of fish in the environment, damaging the epithelium (or lining). Basically, after exposure to aluminum oxide, your fish are unable to breathe in enough oxygen and exhibit delayed survival reflexes.

The gill epithelium is responsible for the gas exchange of oxygen and carbon dioxide – so logically if there is damage to this lining, a whole host of issues can follow. Hypoxia (oxygen deficiency), hypercapnia (increased carbon dioxide levels in the bloodstream), and acidosis (acidic conditions in blood and tissues) can all prove quickly fatal to fish in your tank.

In a waterway such as a river or ocean, fish can survive where rusted aluminum cans have been discarded. This comes down to the volume of water diluting the toxic aluminum oxide particles to a level that is no longer harmful to the fauna in the area. With a smaller volume of water (eg. an aquarium), the dilution does not occur to the same degree.

And if I’ve already added Aluminum to my tank?

If you’re noticing some of the above symptoms in the fish in your aquarium, it’s worth investigating whether aluminum poisoning could be the cause. Most features specifically build for fish tanks are free of toxic metals, however cheaply made products or DIY projects that you’ve added to your tank may accidentally contain aluminum or other poisonous metals.

Simple tests of your water quality can be conducted to assess aluminum levels – if they come back with a high reading the next step is to find the source of the aluminum oxide. Have a look around your tank for any equipment or decorative features that could contain dangerous metals, and remove them to prevent further contamination of your water.

Conduct a water change to eliminate harmful levels of aluminum oxide from your tank (even when you’re not suspicious of metal poisoning, regular water changes are imperative for the health of your aquarium). If you can get in contact with an expert, ask them if they can recommend any products that can be added to your tank to bind to aluminum oxide particles and filter them out.

What can I use in my tank instead of Aluminum?

So we know that a vast majority of metals are reactive and dangerous in your fish tank, but are there any that you can safely use if you like the aesthetic of metal features? The answer is yes!

While aluminum has a high affinity for oxygen, there are other metals that take a lot longer to oxidize and can be used in your fish tank for short periods of time.

Stainless steel is resistant to corrosion in freshwater, so it will take a lot longer than other metals to break down. Eventually, it will oxidize and corrode, which is something that you will want to keep in mind, and keep an eye on if you’re planning on using it over the long term (eg. to screw down pieces of driftwood).

Titanium is an inert element, meaning it is not chemically reactive and will not oxidize in your tank. It does tend to be a more expensive option than stainless steel but is fine to use over the long term.

If you don’t want to spend a fortune or are worried about corrosion over the long term but still want a metal look in your aquarium, most metals can be coated in a plastic film or resin to protect them from reacting with their environment. There are also plenty of other materials that are completely safe to use in an aquarium such as untreated wood, glass, ceramic, and plastic.


These days with so many options in decorative features and accents for your aquarium, it’s not difficult to find a substitute for aluminum and reactive metals that is guaranteed to not harm your fish. 

Regularly testing your water quality is an effective way to ensure that your aquatic flora and fauna can thrive in your aquarium. This way you will have the statistics on the metal concentrations in your tank, as well as other helpful indicators such as pH.

Doing your research about features you are planning to add to your tank goes a long way in protecting your fish. Find out what it is made of, and if it does contain a reactive metal does it have a protective coating that stops dangerous particles from entering the water?

Overall, ensure that you are aware of what is safe, and what is unsafe to add to your tank before you decide to add anything to your much-loved aquarium, ensuring that it will last and be enjoyed for a long time to come.