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Is Rust Bad For Aquarium Fish? : Avoid It or Remove It?

Is Rust Bad For Aquarium Fish? It is a common question I hear from many aquarium owners who wish to put some metal objects to decorate their tanks, and we are going to talk about it in this article.

What Is Rust

If you submerge metal in your aquarium for a long time, it will rust after a while. Metals cannot tolerate submersion in the water for a long time.

Eventually, they start to react with water and create metal oxide, which we generally call Rust.

Is Rust Bad For Aquarium Fish

Is Rust Harmful For Fish

Rust is not harmful if your tank has small percentages of them. However, they can be harmful if your fish are being exposed to higher levels of metal oxide.

Fish can suffer from metal poisoning, causing them to die after some time. So, it is vital to keep the Rust away from your aquarium by following every possible way.

How Rust Harmful To Fish

Rust is actually iron. Rust can enter into your aquarium from rusting pipes that deliver water to your tank or as a result of metal items being placed in your tank.

Small percentages of Rust are not harmful to fish because they can filter them back out from their gills. Small percentages of Rust are actually beneficial if you have live plants in your aquarium.

However, if the tank contains heavy amounts of Rust, fish tries hard to filter out Rust, but they eventually fail.

This high concentration of metal causes metal poisoning in the fish and makes them sick.

Unfortunately, metal poisoning is very difficult to diagnose. As a result, your fish may die because of a mystery illness, and you may not be able to save them no matter what treatment you give to your fish.

How To Identify If A Fish Is Poison By Rust Or Not

Identifying metal poisoning is difficult because you may misdiagnose it with another illness. However, when a fish is poisoned by Rust, it shows some signs and symptoms.

  • Your fish eyes get cloudy
  • It shows the difficulty in breathing
  • The color of your fish changes
  • Sometimes the fish dies suddenly without showing any symptoms

As you can see, the signs and symptoms are similar to bacteria and other infections, and you may treat them with antibacterial or antiparasitic medicine, not knowing they are suffering because of Rust.

If you notice a number of your fish dies one by one even after treating them with some medication, you should immediately check out your tank’s water condition.

A high metal concentration is toxic to fish, and it causes problems with the slime coat and nervous system, eventually causing death.

As it is difficult to find out the actual cause for your fish symptoms, the best way is to check whether the water in your tank has visible Rust or discoloration. 

Is Rust Harmful To Plants

No. Rust is not harmful to your aquarium plants. Aquarium plants actually need iron to thrive. As Rust is iron oxide, Rust is actually beneficial to aquarium plants.

The same is valid for gardening plants. Metal rust in the soil is a valuable nutrient for all kinds of plants.

How Rust Form In Tank 

Rust may come from rusting pipes when you use it to fill up your tank through them.

If you keep metal decorations, low-quality filters, motors, air pumps, and other equipment that have poor quality metal sealers and any other metal objects in your tank, rust forms after some time.

When iron materials are exposed to water for a long time, iron reacts with oxygen in the water and forms iron oxide (Ferric Oxide).

We call this element as Rust. Rust’s color is orangish brown. So, when Rust is mixed with water, the water gets discolored.

How to Remove Rust in Metals

If you intend to keep your metal objects in your fish tank and they have already rusted, you have to remove Rust for your fish’s sake at least.

There are several methods to remove Rust in metals. First, take the rusted metal away from your fish tank. And then, try using one of these methods to remove Rust.

Clean the metal with Fiber Wheel Abrasive Buff Wheels

Attach Fiber Wheel Abrasive Buff Wheels into a rotary tool and set the speed to approximately 7,000rpm.

Then gently move the abrasive across the metal, and within seconds the Rust will be gone. Do not forget to wear protective gear before you start cleaning the metal.

Clean with Abrasive Rubber Polishers

Attach 500 grit EVE Technic Polisher into a rotary tool and clean your metal with it. As with Buff wheels, you have to wear protective gear before cleaning your metal.

If you want to get the shine back in your metal, you can use a finer grit rubber polisher after cleaning Rust.

Salt and Lemon Juice or Vinegar

Acidic solutions like lemon juice or Vinegar work well in removing Rust when mixed with salt. Mix salt and Lemon Juice or salt and Vinegar together and apply to the rusted area.

Leave it aside for about 5 to 6 hours, and then you can remove Rust with a tissue or a cloth easily.

Baking Soda(Bicarbonate of Soda)

Make a paste of baking soda with water or Vinegar and apply it over the rusted metal. Leave it for about an hour or so. Then clean it off with a brush.

How To Avoid Rust In Aquarium

Avoiding Rust is easier than you think. The simplest way is to avoid equipment and decorations that are made with metal.

If you suspect the water contains Rust, you can filter them first with a home water filtration system before adding them to the tank.

Your tank already contains Rust mixed water, perform at least 80% water change to be safe. If you already have rusted metal in your tank, remove them from the tank.

If the rust build-up is small, you can just scrape them and remove them from the tank. As I said before, small amounts of Rust are ok for your fish.

How To Check Rust In Tank

Rusted metal looks orangish-brown, and Rust mixed water looks the same but in a lighter color. When a small percentage of Rust is mixed in water, you won’t notice it at all.

Is It Bad To Put Metal In A Fish Tank?

If the metal is covered with aquarium-safe paint or non-toxic epoxy paint to prevent Rust and corrosion, you can safely put it in a fish tank. But the problem is most paints available in the market are non-transparent.

So, you won’t get a metal look in your metal if covered with paint.

There are exceptions, however. Stainless steel is a stainless metal that is known to be aquarium safe.

Titanium and platinum are truly inert metals, so they will not oxidize inside water. So, if you must, you can use either stainless steel, Titanium, or Platinum in your fish tank.

The Difference Between Rust and Brown Algae

Rust and brown algae look almost the same in an aquarium. Some people misjudge Rust with brown algae. So, it is essential to know the difference between rust and brown algae.

Rust and brown algae both look in the same color, which is brown. Rust forms on metal surfaces, and brown algae forms on any surface, including metal.

So, if you have some metal objects in your tank, you may mistakenly think of Rust as brown algae. Hence knowing how to check the difference is essential.

While brown algae are harmless to your fish, Rust can be harmful to your fish. Brown algae quickly come off when rubbed or wiped off.

But, Rust doesn’t come easily when rubbed. You have to scrape the metal object to remove Rust.

However, scraping will leave scratches on your metal objects, and there are other easy methods to remove Rust safely.

Whatever you do to remove Rust from your metal object, you should wash thoroughly before putting them back in the fish tank.

Better yet, replace the object with other equipment if you want your fish to be safe.

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Does Rust kill fish?

Rust is toxic if exposed to higher concentrations of Rust. When fish have to filter off more Rust from their body, they get sick with metal poisoning.

Unfortunately, there is no known cure for metal poisoning in fish. The fish who get sick with metal poisoning dies. The only way to save the fish is to prevent Rust build-up in your tank.

Does Rust In Water Kill Fish?

Rust in water doesn’t kill fish if the rust percentage is small. But if the water contains a higher rate of Rust, it can kill fish. If fish survive through elevated concentrations of Rust, they are extremely lucky.

So, please don’t let them suffer more. Change water immediately and remove any rusted metal objects in your aquarium.

Will Metal Kill Fish?

Yes. Metal can kill fish. Rust and other metal oxide forms are also toxic to fish if they are dissolved in higher percentages.

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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.