Do Pond Lights Affect Fish?

The idea of a beautifully-lit pond gently illuminated at night is definitely idyllic.

If your pond is full of happy fish, it is a calm and serene spot where you can relax and enjoy your carefully cultivated wildlife.

But do those ideas actually clash a little? For example, is it OK to have pond lights if you’re keeping fish, or will you cause them problems?

Pond lights are OK to use with fish, provided they are switched off at night to maintain the day/night cycle. They shouldn’t warm the water or be so bright that they illuminate the entire pond and make fish easier for predators to see.

There are a few things to break down here, so let’s look at:

  • Whether pond lights are bad for fish
  • How to stop pond lights from bothering your fish
  • How long you should leave pond lights switched on for each day

Are Pond Lights Bad For Fish?

private pond in evening

There are a few different ways that pond lights can be harmful for your fish if you don’t use the right type or don’t set them up correctly.

Firstly, there’s the issue of day/night cycles. Like most other animals, fish like to have some time when they can rest at night.

And having a lot of light can disturb that, just as it would if you had the lights on in your bedroom.

If you install pond lights, make sure you can easily control them to switch them off – ideally on a timer, so you don’t have to rely on your memory every night.

Secondly, some pond lights can generate heat, mainly if you use halogen bulbs.

If you have multiple halogen bulbs, you might alter the entire pond’s temperature, heating it up and making your fish uncomfortable.

Next up, some fish also don’t like to be exposed and are aware when they’re in a well-lit space.

If you light up the entire pond, your fish may be distressed, which can manifest as physical illness.

That’s also an issue if you have fish that could be attacked by a predator.

Whether it’s smaller fish that birds may go for or even larger fish that might be attacked by raccoons, coyotes, or foxes, if you have pond lights making the pond glow, it’s like a neon sign at an all-you-can-eat buffet.

Finally, while pond lights are artificial, they can still help certain forms of algae to grow faster.

This can make your pond harder to keep clean, making it more of a health hazard for your fish.

Do LED Lights Hurt Fish Eyes?

Koi fish in a natural stone pond

Fish are not particularly sensitive to types of light.

They care about brightness and heat, but not the different light colors or wavelengths.

So LED lights won’t hurt fish eyes, provided you ensure they aren’t too bright.

Even that shouldn’t be an issue, though, because the water will act as a natural detractor of the light, reducing the brightness.

Provided you haven’t purposefully bought the brightest bulbs that you can, your fish shouldn’t have any issues.

How To Prevent Pond Lights From Bothering Fish?

View of small pond, trimmed bushes and small waterfall

We’ve established what problems pond lights can cause fish – but that doesn’t mean fish and pond lights are incompatible.

Here’s what you need to do to ensure your fish aren’t bothered by your pond lights.

Firstly, make sure there’s a timer wired on the circuit so that the lights automatically turn off at night.

This will keep the day/night cycle working as it should, and give your fish the right amount of time to rest.

It also means that you aren’t encouraging algae to grow more than it usually would, so your pond maintenance doesn’t have to increase beyond normal.

This will keep your pond cleaner, which is better for your fish.

Next, make sure you’re using LED bulbs.

There are loads of reasons why LEDs are better than halogens, including the fact that they’re much longer-lasting.

But the reason here is that they don’t generate anywhere near as much heat, so they won’t cause the pond temperature to rise.

The fact that LEDs don’t hurt fish eyes means there’s no reason to consider an alternative, except for cost – and LEDs aren’t that much more expensive anyway.

Next, plan your pond layout to make sure that there are dark spots where the fish can hide when they want to.

Don’t make it so that your entire pond is lit-up at all times.

Adding hiding spots can also help fish avoid predators, or you could ensure you only use the pond lights when you’re outside.

That way, there’s no wasted energy – the lights are only on when you’re benefiting from them – and predators are less likely to attack with a human hanging around.

You could also cover the pond to protect your fish, but most people avoid this as it can spoil the aesthetic.

What Is The Safe Cycle To Turn The Lights On?

Pond in a beautiful creative lush green blooming garden

In the wild, fish are generally used to an average of at least 12 hours of daylight.

But if you want to enjoy your pond in the evening, most fish species will also be able to cope with a couple of extra hours of light.

While there are published guidelines for aquarium fish, where you can control the light levels a lot easier, there aren’t any specific recommendations for pond fish.

So it would probably be best to aim for 8-10 hours of darkness a night, depending on the season.

In summer, you might not get a full 8 hours of total darkness, but try to make sure your lights are off from around 11pm until morning.

Final Words

There’s no harm with adding pond lights to an inhabited pond, provided you follow all of the steps above.

Most importantly, make sure your fish have time without the lights, and they’ve always got places to hide if birds start hovering overhead.

What fish do you have in your pond, or if you’re planning your pond, do you have any species in mind?

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