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Can You Put Metal In A Fish Tank?

After we published our article going over if you can use stainless steel in a fish tank, we have noticed more and more questions from people within the fish keeping community about using various types of metal in their aquariums for a wide range of different use cases.

Due to this, we have decided to publish this article going over if you can put metal in a fish tank or not to try and help as many people as possible who are curious about using various types of metal in their tanks.

We would never recommend that you use any type of metal in your fish tank that is submerged for long periods of time.

Even if the metal does not rust, there are other problems that metal can cause in a tank that may end up causing problems for your fish so the risk is just too high when there is often a plastic option available in most cases.

We have noticed a spike in the number of people who are using toys or tabletop battle figures as tank decorations within the fish-keeping hobby with many of these containing metal too.

Although some of these are made of inert materials that shouldn’t cause a problem, the ones with metal on them can definitely be problematic and should be avoided if possible.

Can Metal Harm Fish?

Metal can end up harming the fish in your aquarium due to causing potential problems with your aquarium’s water parameters while also potentially releasing toxins into the water if the metal rusts. Even small amounts of metal are often enough to cause these problems so we recommend people avoid using metal in their tanks at all costs if possible.

Even aquarium tools that are only temporarily used when cleaning an aquarium can end up causing problems if the metal is not dried after use and begins to rust.

These small rust particles can develop on the tool and sit until the next time that you use it in your tank only for the rust particle to fall off the tool and end up hiding in your aquarium somewhere causing problems.

We have seen a number of reports on social media of people who have had this exact problem with their own aquariums due to small pieces of rust falling of cleaning tools and blending in well with their substrate.

Not only can this release toxins into your aquarium water but it can also warm your water parameters and due to the rusted metal still being in your tank, your water parameters will end up shifting back to the problematics ones quickly after doing a partial water change in your tank to try and fix the problem.

Can You Put Gold In A Fish Tank?

The general consensus is that pure 24 carat gold is fine in freshwater, it can still end up causing problems in your aquarium over time.

The majority of people in the fish keeping hobby often use a lower grade of gold with 22 carat and everything below it actually being an alloy of gold with other metals added that may end up causing problems with your tank.

Most investment grade gold will use copper or silver as the alloy metal with jewelers grade gold alloys often using copper and other metals to keep the costs as low as possible.

This is why we usually recommend against adding any gold to your fish tank even if you are confident that it is pure 24 carat gold as it is not worth the risk.

We know that the pirate treasure chests are a popular tank decoration right now but some of the cheaper ones simply have painted metals as the gold in the chest rather than real gold.

This is commonly copper with gold paint on it and although copper does not rust, it can cause other problems in your aquarium once its patina starts to form and the copper reacts with your aquarium’s water.

Can You Put Brass In A Fish Tank?

There was a time when brass was commonly used as a fixture or fitting for aquarium tanks but the hobby has since evolved and it is commonly accepted that brass can cause problems with your aquarium water and should be avoided.

Brass is made from copper and zinc and once the copper reacts with your tank water and its patina starts to form it is usually too late to do anything about the potential release of toxins in your tank’s water.

It is very rare that brass will be used as a fixture or fitting in a modern aquarium due to this and most brands who make aquariums will use another material.

There are some aquarium decorations on the market that contain brass on them and we would recommend against using them in your own aquariums if possible.

We have seen some people on social media report using a cast brass figure in their aquariums as a decoration without issue.

Although this could be true, it is more likely that the brass is causing problems with their aquarium water conditions and that their fish simply aren’t showing any symptoms yet.

In addition to this, the more robust species of fish may not show any obvious symptoms and still be able to live for years with minimal issues.

Can You Put Aluminum In A Fish Tank?

Using aluminum in a fish tank is controversial and does tend to divide the fish keeping community on its use within tanks with a pretty even split.

Arguments can be made both for and against using aluminum in a fish tank but our general rule of thumb is if there is a strong case against doing something then don’t do it.

This will depend on exactly what you are thinking of using your aluminum for though and many people within the hobby do use it within their tanks with minimal issues.

Many people keeping large tanks with expensive fish in them choose not to take the risk though as any metal used in a fish tank can present a small level of risk.


That brings our article going over if you can put metal in a fish tank or not to an end. As you can probably guess by this stage of the article, we really wouldn’t recommend that you do it as the risk is often more than the potential reward as there are plenty of inert materials that you are able to use within your fish tank that shouldn’t cause issues and offer a very similar level of performance to the various metals that people use.