How to remove hard water stains from an aquarium

Hard water stains often form on the top of an aquarium tank. This is likely due to the effect of the evaporation of hard water. The leftover residue is typically due to mineral deposits that accumulate on the glass, which is known as “limescale.”

When water evaporates, it leaves behind mineral elements that stick to the aquarium glass. This results in an undesirable white residue left behind. For those who live in a house with hard water, the same build-up can occur in the shower.

Although the residue will not harm your fish or the aquarium, it will make the glass appear foggy or streaking so it’s more difficult to see the fish. Read further to learn how to remove hard water stains from aquarium. 

Indications of calcium buildup

The buildup of calcium, or limescale, can produces white, crusty-looking streaks and spots on the inside of an aquarium, along the edges, on the filter or even on the hood.

Calcium is naturally present in water, so fortunately, its buildup will not harm your fish. The main problem with limescale buildup is that it’s not nice to look at and can ruin the appearance of your aquarium tank.

What are the causes of lime buildup?

As we mentioned, the buildup of calcium is caused by the mineral residue left on and in the aquarium as the water starts to evaporate. Once the minerals build up on the glass, the white streaks and spots will begin to accumulate on the interior of your tank, the filter, the lid, and other elements. This especially happens at the level of the water where it evaporates. 

If you live in an area with hard water, the buildup of calcium is more likely to occur. Hard water contains higher mineral levels than soft water, so one way to avoid water stains on your fish tank is my purchasing a water softening filter for your home. 

Video: Removing Hard Water Stains from An Aquarium

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How do you remove calcium deposits from glass?

The buildup of calcium deposits or lime can be undesirable to look at and some might be tempted to use some home cleaning products. Nevertheless, this is not advisable in a fish tank.

Even a tiny amount or extra deposit from any cleaning product can be deadly to your fish. This rule applies to the top edges of the tank as well.

The vinegar method

There are safe products that can safely remove lime buildup from an aquarium tank. For a safe alternative, use plain white vinegar on a dry aquarium. Vinegar is not only an organic disinfectant but it also dissipates stubborn deposits of lime. Let’s take a look at the steps for cleaning with vinegar.

1. Transfer your fish to a temporary holding tank 
2. Completely drain the water from the tank and remove any decorations or plants. 
3. The gravel or sand can be removed or left behind if it’s covered with something to prevent the vinegar from spilling. 
4. Put the tank on a towel or absorbent cloth. If the tank is too big to move, have towels on hand.
5. Pour or spray vinegar solution (1:1 vinegar-water ratio)on the glass. 
6. Let is soak for 10-20 minutes and brush with a non-abrasive cloth or pad.
7. In case there is a persistent patch where lime accumulates, try using a razor blade or algae scraper to scrape it away gently. 
8. Rinse out the tank carefully before adding new water. 

How do you clean dirty fish tank glass without using any products?

An aquarium requires regular cleaning and maintenance to keep it clean and free from any debris.

It’s very important to note that you should never replace the fish water 100 percent. When you transfer the fish to a different container, use some of the original water from the tank to minimize stress on the fish. 

Leaving at least 24% of the water from the tank will ensure that you don’t remove the essential bacteria that your fish need to survive. Putting fish in brand new water can be shocking to them, and even cause them to die.

Follow these steps to learn another way to clean a dirty aquarium tank.

1. Unplug everything in the tank, including the filter, aerator and heater. 
2. Remove all decorations and electrical devices from the tank.
3. Put the fish in another container (with “dirty” water from the tank).
4. Use the water siphon or hose to remove the dirty water and vacuum debris from the gravel. Carefully vacuum the gravel with the hose to get rid of fish waste and leftover food.  
5. Leave at least 25% of the water in the tank.
6. Wipe down the interior of the glass with a paper towel or clean rag. Avoid using any cleaning chemicals since it can be harmful to your fish. Rinse off any decorations with water. 
7. Return all decorations, the aerator and heater.
8. Start to refill the tank around 90% full to provide enough space for the salt and water conditioner if you have a salt water tank. You can now plug in all electrical devices. 
9. Add salt and the water conditioner if necessary. Allow the tank to sit for 15-20 minutes to balance out the water temperature.
10. Return the fish to the newly cleaned tank. 

It is recommended to clean the aquarium tank every other week.

How to prevent hard water stains in an aquarium

Hard water stains in an aquarium can be avoided by preventing the minerals from being deposited in the first place. Since evaporation is responsible for the formation of this residue, check the waterline of the tank every 2-3 days.

Things like low humidity during the winter or warm water temperatures can drive up the evaporation process. 

Once the water starts to evaporate, the water remaining will become harder with a higher mineral concentration. That’s why you should replace evaporated water with distilled water, to balance out the high mineral content. 

Although you should use regular hard water to fill the tanks of certain fish, replacing the evaporated water with mineral-rich water can steadily lead to a lethal increase in some minerals. Using distilled water eliminates this risk.

Frequently asked questions about cleaning an aquarium

Final thoughts

Hard water stains in an aquarium tank can be undesirable to see. Luckily, with the methods discussed on how to remove hard water stains from the aquarium, you can easily deal with this type of stain effectively.