Do Candles Affect Fish? Are They Aquarium Safe?

Candles are big business in our modern world. From humble beginnings as a purely functional means of providing light, the global candle market is positively booming. From artisan online brands to the multipack you pick up in the grocery store, it can seem like they come in every scent imaginable.

What may not spring immediately to mind when reaching for the lighter, is the impact these little sweet smelling twinkly delights could have on your unsuspecting fish happily swimming around their aquarium.

Burning any candle will disperse particles into the air which may have implications for your filter choice. Scented candles present more of a concern but as the impact is unknown, we advise using candles minimally around aquariums and only burn heavily scented varieties in other rooms where possible.

What are Candles Made of?

Candles can vary widely in design, scent, and material but there are certain key components. A candle, by definition, is a block of wax or animal fat (tallow) with a central wick that will exude light as it burns.

Are There Different Kinds of Candle?

If you asked the majority of people what makes up candles, a fairly vague response of “wax” would definitely score highly.  That is not wrong but there is a huge variety of wax out there, each with its own specific properties.

In addition to wax, there are also candles comprising in part or full of fats or oils. A list of the main candle types is outlined below:

Paraffin – a derivative of petroleum. This is the most prevalent wax type, largely due to its ease of processing and its availability of it which makes it cost-effective.

Animal Fats – largely unheard of now, the earliest candles occurred when the ancient Egyptians discovered they could melt down animal fats to be utilized in candles. This burned with a smoky flame and an often unpleasant odor.

Beeswax – this utilizes the wax bees produce as part of building their hives. This has been used historically for centuries since humans discovered that beeswax burned without smoke and had a more pleasant aroma than previous animal fat candles.

Soy – this is a wax derived from treating soybean oil. This has been rising in popularity as an ethical alternative to paraffin wax.

Gel – this is a candle type where mineral oil such as paraffin oil is combined with a small amount of resin to change the consistency to be more gel-like.

Palm – this is an oil-based candle type utilizing palm kernel oil.

Are Candle Wicks Toxic?

While we must pay attention to what wax or substance is used in a candle for the most part the wick should be of fairly low concern. Once upon a time lead was used to stiffen candle wicks. However, this was linked to possible lead poisoning as the fumes were released and this has now been banned in the United States, Europe, and other countries so you are unlikely to come across it now.

The by far most common option of the wick is cotton; this is due to its ability to burn without smoke and minimal by-products. Occasionally a cotton wick can be stiffened with a fine wire, usually copper. However, the amount is so negligible it is unlikely to cause a health risk.

That being said, burning even the smallest amount of cotton will create soot, tiny particles of burnt matter that float in the air and can be inhaled or settle on surfaces. While it may not be visible to the naked eye, burning multiple candles for a prolonged time would increase the soot floating around and settling in an enclosed space.

What Gasses or Chemicals do Candles Give Off?

You wouldn’t want to run a diesel engine in your lounge, but it may be surprising to learn that many of the toxins released by burning a widely available domestic paraffin wax candle are similar to those found in diesel fuel emissions.

Now before you start gasping for breath, remember this is in much smaller volumes than a car but they are still there. The collective term for the released toxins is volatile organic compounds or “VOCs”. As both paraffin and diesel are derived from crude oil, they share certain chemicals when burned such as acetone, benzene, toluene, formaldehyde, and acrolein.  

The other big culprit of nasty air particles is the by-products of certain chemicals used in the creation of synthetic fragrances. Often cheaper candles will use chemical alternatives to enhance or replicate natural scents. Many of these create their own VOCs when burning.

Alternatives such as plant-based waxes of soya or palm oil have lesser by-products and may be better for air quality.  Picking ones that are naturally scented will improve air quality further.

If you are determined to still burn a candle but want optimum air quality, unscented beeswax with a cotton wick is the gold standard. As beeswax is naturally occurring it burns cleanly and achieves a very high heat which nearly completely incinerates the cotton wick with minimal soot or ash.

What Types of Aquaria Are There?

There is an absolute plethora of choices when it comes to the size and type of aquarium with each variety tailored to the fish and/or aquatic plants intended to live in them.

The first starting point is freshwater, cold water, or saltwater. It will depend on the fish you intend to keep but either way, both will need some sort of filtration.  Plants can help with filtration in freshwater tanks while you may consider some sort of coral to aid in saltwater.

Coldwater tanks will require systems to maintain a cool water temperature whereas saltwater tanks are commonly kept warmer for tropical fish.

Unless you want to be changing your water constantly nearly every aquarium will include a powered water filtration device. There are options for filter material, however, charcoal filters are widely accepted as the crème de la crème and would be strongly recommended for use in rooms where air quality could be compromised.

Will Different Fish React to Different Toxins?

In short yes, but specifics we cannot be sure of. Just as in nature some fish can survive in murkier water quality than others the same goes for aquaria.

There is no specific data on the impact of candle by-products on individual aquatic life however we do know that fundamentally, particles such as soot and other toxins will make your filtration system work harder.

What Will Happen if the Candle Falls into the Tank?

In this case, the water will put out the flame. However, allowing the candle to stay submerged in the water allows chemicals and toxins to leach into the water.

This has a high chance of impacting the water quality and introducing bacteria into the water which may prove detrimental to your fish. If this does occur, with a candle or any other foreign object, then the item should be removed and the water and filter changed,

What is the Optimum Distance Required to Keep Fish Safe When Burning a Candle?

There is no definitive guidance on this and as we have outlined there can be many factors such as the composition of the candle and things like overall ventilation in room size.

In the spirit of being cautious, it would generally be advised to avoid burning candles in the same room as your aquarium. If a candle is a necessity choosing a beeswax option and limiting the size and burn time is likely to be the least impactful for your overall air quality and as a result, keep your fishy friends safe.