Could a scented candle be a danger to my fish?

68e15ed0-47f2-41ee-94d8-a081d17c2455

Editor's Picks
Features Post
The brightest pupils
04 October 2021
Features Post
Dealing with egg ‘fungus’
04 October 2021
Features Post
Rathbun’s tetra in the wild
13 September 2021
Fishkeeping News Post
Report: 2021 BKKS National Koi Show results
13 September 2021
Features Post
The World's forgotten fishes
16 August 2021
Neale Monks explains the potential risk of scent in the same room as your aquarium.

Q: Please could you tell me whether a scented candle might affect my fish? I’ve just had four fish die on me – two Bleeding heart tetras and two Yoyo loaches. I tested the water and the results were okay, but I carried out a 25% water change anyway. The other fish still looked unhappy, however, so I’ve added charcoal to the filter in the hope that it will remove anything nasty that might still be in the water. Please could you advise?

BRIAN SADLER, VIA EMAIL

A: Neale says: Without knowing exactly what was in the candle, it’s impossible to know for sure what happened here. However, your response — substantial water changes and the use of activated carbon — is spot-on, and if you do some more water changes over the next few days, the remaining fish should recover. If you add a little extra aeration, that’ll help as well, especially if the toxin affects the way that blood carries oxygen.

Broadly speaking, anything you can smell in the air has to be considered a potential risk — whether scented candles, room freshener, cleaning products, paint, or anything else giving off airborne chemicals. With that said, many such products are perfectly safe, and described as being ‘pet safe’ or low VOC/VOC-free (where the VOC part refers to volatile organic compounds, the most like chemicals to cause problems for your fish).

If you use any products with an airborne component — perhaps an odour of some sort, or else something you spray into the air — you need to be more circumspect. I don’t worry too much about using a bit of furniture polish in the same room as my fish tank, but if I was doing something like painting the walls, I’d be more cautious. And if it was something I didn’t need to do at all, like use an air freshener or scented candle, I’d simply use those items in another room.

I think you’re unlucky, more than anything else, and regular candles certainly don’t cause fish to die. I think that it was highly likely something was a bit off with that particular brand or scent. But lesson learned, I suppose, and I hope the remaining fish recover quickly and you can get back to enjoying a happy and healthy aquarium.