How To Prevent Calcium Buildup On Fish Tanks – 5 Simple Strategies

We had a scare one day when our six-year-old informed us that our fish tank had turned frosty. It was winter, but we had a tank heater. Needless to say, we realized that the “frost” was calcium buildup. 

If you’ve already tried to remove calcium buildup in your aquarium, you know it’s a labor-intensive task. So, we’re sharing strategies for how to prevent calcium buildup on fish tanks.

The Cause of Calcium Buildup On Fish Tanks

Before we talk about how to prevent calcium buildup on fish tanks, it’s helpful to understand the root cause.

Calcium buildup occurs in fish tanks because of hard water. Many fish prefer hard water, so having calcium in the water isn’t necessarily a bad thing. But you should use an aquarium test kit to determine where your water falls on the hardiness scale to ensure it’s in a safe range for the fish species your family owns.

It’s common to notice calcium buildup on your tank’s glass and fish appliances, such as the hood and filter, in areas where the water has evaporated.

Strategies for How To Preventing Calcium Buildup On Fish Tanks

When it comes to cleaning your tank or even removing scratches, you may have already realized that taking steps to keep your tank in good condition to start with, can save you time, effort, and money down the line. Now that you know why calcium accumulates in your aquarium let’s explore how to prevent calcium buildup in fish tanks.

1. Refill Water Often

Since calcium buildup primarily appears after the water begins evaporating from a tank, keeping your aquarium topped up with fresh water is one of the best prevention strategies.

The frequency you’ll need to refill your tank varies according to the weather. For example, hot and dry winter weather will spark faster evaporation. You might find that topping off your tank water every two to three days is the ideal balance.

Unlike tank changes, it’s best to use distilled water for these small refills. That’s because the concentration of calcium and other minerals will increase as water evaporates. So, distilled water won’t add fuel to the fire by creating more minerals that can become buildup in your tank.

2. Use a Filter

A high-quality filter is vital for removing excess minerals in your fish tank, including calcium. There are three primary filter types:

  • Mechanical 
  • Biological
  • Chemical

Whereas mechanical and biological filters are vital for all aquariums, not all fish keepers use chemical filtration. However, a chemical filter is beneficial since you’re struggling with calcium buildup in your tank.

Chemical filters work by dissolving and then trapping minerals and other waste. Activated carbon is the primary substance chemical filters use to perform this function.

The good news is that you might not need to buy an entirely new filter. Instead, many filters offer the option to add a chemical filtration system to the mechanical and biological functions it already has.

3. Purchase a Water Softener

If your water hardness level is higher than recommended for your fish, you can buy an aquarium-safe water softener to manage the issue. As a result, there will be less calcium in your tank that can turn to buildup.

Even though it’s tempting to reduce the hardness of your water significantly, proceed with caution; many fish require hard water to survive.

For this reason, you should use a water hardness kit to monitor how hard or soft your water is, especially after you perform routine partial water changes.

4. Add Driftwood

Placing a piece of driftwood in your aquarium can help prevent calcium buildup because driftwood neutralizes carbonate compounds. It does this by releasing specific acids that help naturally soften the water.

Another benefit of driftwood is that it introduces tannins in the water that are beneficial to your fish’s health.

That said, driftwood can turn your tank water a bit brown. It can also carry parasites if you don’t treat it before introducing it to your tank. (Consider whether you should quarantine newly acquired driftwood.)

5. Change Your Filter Media

Several types of filter media exist on the market. But peat moss is among the best option for fish keepers struggling with calcium buildup.

Peat moss works by softening water by demineralizing it through chelation, which binds calcium ions together. It’ll also bind magnesium ions, another common mineral culprit that can lead to white calcium-looking deposits on the side of your tank.

Chelation has such a powerful effect that it can even help detoxify dangerous metals like arsenic and lead.

How To Prevent Calcium Buildup On Fish Tanks

You’ll need to prepare your peat moss by boiling it for three minutes to ensure it isn’t carrying parasites or other chemicals that could harm your fish. We also recommend soaking it in distilled water. Otherwise, it could turn your tank water a yellowish-brown color.

If you’re not keen on changing your filter media, you can let peat moss float inside your tank. Doing so will still help prevent calcium buildup. 


Several strategies can reduce or eliminate calcium buildup in your aquarium. Select any one of the above suggestions to help keep your tank looking clean and clear.

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