Most people (myself included), will keep fish for more than one reason. A common reason for keeping fish though is for the decorative and visual appeal that they give to a home or room.
Not only are certain breeds of fish favored for their vibrant and visual appeal but decorating a fish tank allows fish keepers to add their personality and design to the tank. While plants, substrates, and decorative ornaments are go-to options for most people, the materials you put into the tank can often be an afterthought.
With this in mind, there’s some science and good practices when it comes to decorating a fish tank to ensure you don’t cause the fish discomfort or ill health. One particular topic that I want to cover in this article is whether or not you can put metal objects in a fish tank?
Read on to get the definitive answer…
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Can You Put Metal Objects in a Fish Tank
Research shows that heavy metals such as mercury, copper, lead, and zinc are extremely dangerous for the health of fish and when water is polluted with these types of metal, it can end up being very toxic and poisonous for the fish.
Now you might be thinking that this is not really relevant to your home aquarium and really, you were just planning on putting more “every day” metals in your fish tank for decoration. These metals will usually be stainless steel, aluminum, or some other metal used for commercial purposes.
While not a heavy metal, the question is therefore can you put metal objects in a fish tank, and are there any exceptions?
No, you cannot put metal objects in a fish tank. Metals will react with the water over time and start to corrode and oxidize which will lead to toxins being released into the fish tank which will ultimately be poisonous to your fish.
Much like the example and research I’d covered above, the issue with most soft metals is that they will eventually corrode and rust. When this reacts with the tank water it releases oxides which are then poisonous to your fish.
Why You Shouldn’t Put Metal in a Fish Tank
I’m sure many of you reading this will wonder why you shouldn’t put metal in a fish tank. We see metal in the lakes and oceans all the time with fish making homes out of sunken ships and discarded cans (though the ethics of these items being in the wild are a whole separate topic!) without it seeming to do them any harm?
The key thing to keep in mind though is water quality is dependent on water volume. More experienced fish keepers will know that smaller tanks at 1 – 5 gallons are much harder to maintain good water quality, especially if you are keeping too many fish, and regular water changes and gravel vac sessions are essential.
When metal corrodes in the water in the wild, the tide and overall water volume mean the effects on the fish that inhabit that particular area are much less than when a metal corrodes in a much smaller home aquarium.
When metal corrodes and releases oxides into the water in a fish tank, the water quality diminishes rapidly and we know that fish have relatively weak immune systems and most breeds are quite susceptible to changes in water quality.
Therefore, putting metals in a fish tank will always carry the risk of corrosion. This will lead to toxins being released into the water and this will eventually be harmful, poisonous, and even deadly for the fish in the tank.
Rust and corrosion are long-term issues however, there are also some short-term issues that you need to be aware of when keeping metal in a fish tank.
Metal can cause chemical reactions in the water which can directly impact a fish’s natural biology. It can impact the rate at which eggs hatch, it can cause growth defects in newborns, and in some instances, fish in areas of high metal contamination have been known to develop deformities.
If I’m being honest, there are very few benefits to placing metal into a fish tank and the potential risks (while not 100% guaranteed to cause your fish an issue) are enough to warrant not placing any kind of metal in your tank for fear of disrupting the water chemistry and quality.
Are There Any Safe Metals for a Fish Tank
I must admit that metal corrosion is not guaranteed to cause your fish any harm, particularly in the short term before the metal has a chance to corrode and cause any chemical reactions, but does that mean there are some metals that are safe for a fish tank?
The honest answer is no!
While inert metals like stainless steel and titanium are relatively resistant to the effects of corrosion or rusting, they are not resistant to the effects of time. Sustained exposure to water will eventually lead to corrosion and though the timeframe may be longer, the end result will ultimately be the potential for poised water.
Aluminum, copper, iron, bronze, brass, carbon, and any other metal you can think of will, unfortunately, be unsuitable for use in a fish tank as well. I wish there was a solid recommendation I could give and you are likely to see some people on fish forums claim that there are “safe” metals for a fish tank.
This is simply not the case and in 99% of cases, it’s a much safer option to simply not place any kind of metal in your fish tank and eliminate this risk entirely.
Substitutes for Metal in a Fish Tank
If you are new to fish keeping and are looking for some tips to decorate your tank, especially with items that do not contain metal, the video below is one worth checking out for a basic overview of how you can decorate different types of aquariums.
For some other useful tips and ideas, I’ve compiled a shortlist of some of the best things to put in a fish tank for better decoration and as substitutes for metal.
** Disclaimer – before doing any decorating inside your fish tank, first make sure you know what breeds of fish you will keep and what their individual requirements are. These requirements will often dictate what you can, and should, decorate your tank with and it will make the decision much easier.
- Substrate – The substrate on the bottom of your tank is a good starting point and will set the tone for your tank’s theme. Sand, colorful gravel, or even pebbles are all viable options and while some people opt to not have any substrate, most breeds of fish will have it as a requirement.
- Plants – The best thing you can use to decorate your tank is an array of plants and floral features. Plants are not only a natural addition to provide hiding places for certain types of fish but they help oxygenate your tank improving the water quality. From a decorative perspective, they also look impressive, especially when opting for a well-planted tank that creates a small ecosystem.
- Ornaments – This is the category that metal objects will usually fall under so it’s important to know the best kinds to use. Most store-bought ornaments like caves or themed objects will be specially treated for use in a fish tank. If you try to add regular, everyday items that are not purchased specifically for fish tanks, then this is where you will have issues with water quality and potential toxins being released into the tank.
These are the basics when it comes to decorating a fish tank but they are also the most commonly used options for good reason. These forms of decoration are not only safe for fish tanks but in all cases, they help enhance the health or quality of life for your pet fish.
Even an ornament can act as a hiding spot for fish so all of the above serve a purpose and should be used in place of potentially harmful metal objects.
Final Thoughts
I know there is a desire to constantly improve the visual look of your fish tank and make it a standout feature of the room. A well-decorated fish tank is also beneficial to your fish for a number of reasons from providing hiding places and sheltered areas to improving the water quality through oxygen-producing plants.
When it comes to adding metal objects into a fish tank however this is, unfortunately, a bad option and something that can ultimately be harmful and poisonous to your fish. Metal will corrode in water and gradually leak harmful chemicals into the water which can drastically reduce the water quality in your tank.
Therefore, never put metal objects in a fish tank and before adding any kind of object into a fish tank, first, make sure you do necessary checks to ensure it will not cause the fish harm in any way.
