Can A Fish Tank Be Near A Window?

If you listen to some aquarium owners, especially on online forums, you’d think putting a fish tank near a window is one of the biggest mistakes you can make. Most of them cite excessive algae as the biggest issue you will face, with others saying your fish will cook in the sun.

But in reality, it is possible to place a fish tank near a window without killing off the fish or plants. In fact, an aquarium can thrive more with some exposure to sunlight. Here’s what you need to know about putting a fish tank near a window including what precautions to take if you decide to do it anyway.

The Best Place to Place a Fish Tank At Home

There are a few things to consider when deciding where to place a fish tank. There’s is aesthetics. You want the aquarium somewhere where it looks great and you can clearly see it from different angles.

More importantly, you should place a fish tank where the temperature is stable. So avoid placing it close to a heater, a radiator, an AC vent or a fireplace.

Other factors to consider include ease of access, available space, and proximity to a power source for equipment like the aquarium heater and filter.

Most experts and experienced fish tank owners will also generally not recommend placing a fish tank close to a window. But is it really that bad? Let’s first look at the two main issues that could arise from having your aquarium next to a window.

The 2 Main Risks of Putting a Fish Tank Near a Window

The biggest issue many people have with putting a fish tank next to a window is the exposure to direct sunlight. A lot of aquarium owners use artificial lights, making it easy to control the intensity and period of light exposure to the fish and plants.

With sunlight, you have less control. This carries two main risks.

1. Algae Bloom

This is the most cited reason to avoid placing a fish tank near a window. While algae are not plants, they share some similarities including the ability to perform photosynthesis and consume carbon dioxide.

So the presence of sunlight will spur and accelerate the growth of algae. Indeed, if you keep your fish tank near a window where it receives several hours of sunlight, you’ll likely notice more algae growing on rocks, the substrate and on the aquarium walls.

How Bad Is It?

One thing a lot of people leave out when they say sunlight will cause an algae bloom in your fish tank is that algae also depends on other things to grow. Algae also needs carbon dioxide, minerals and water (obviously not a problem) to thrive.

In fact, a lot of the time when a fish tank has an algae problem, it’s because the organic load is too high. Excessive nitrates and phosphates from fish waste, uneaten food, plant fertiliser, decaying plants and other organic matter fuel the growth of algae.

So if you are careful to manage the organic buildup in your fish tank, then exposure to sunlight shouldn’t cause an algae bloom.

2. Temperature Fluctuations

The other worry about having a fish tank close to a window is temperature fluctuations. Most fish survive in a narrow range of temperature. Having your tank overheat during the day and then cool down in the evening is certainly bad for the fish.

How Worried Should You Be?

It depends. Many modern windows are double glazed. They allow sunlight in but not much heat. Having a fish tank next to such a window is not a big deal temperature-wise unless you keep the window open during the day.

Also, that specific window where you plan to put the fish tank probably gets only a few hours of sunshine daily, which may not be enough to heat it up.

That said, depending on the design of your home and your climate, temperature fluctuation could be a real concern. If the room where you have the fish tank gets hot when it is sunny, then it can definitely cause the fish tank to warm up as well. But there are ways to mitigate this, as we explain below.

How to Safely Put a Fish Tank Near a Window

There are many reasons to put a fish tank near a window. It’s probably the only spot available in the room, maybe it looks great there with natural light falling on it or maybe you have some sun-loving plants in your aquarium that grow best with some sunlight.

Whatever the reason, here are some tips on how to safely put a fish tank near a window.

Avoiding Algae Bloom

You don’t need to do anything special to avoid algae. Just up your maintenance schedule to ensure organic matter doesn’t build up too much.

Clean the filter often, clean the substrate and decorations, and do weekly water changes.

Adding more plants to your fish tank can also help manage algae levels.

Note: A little bit of algae is safe for the fish and some fish even feed on it. Algae can also absorb waste products to help maintain water quality and they oxygenate the water during the day. So if you notice some algae, it’s fine. Just make sure it doesn’t become too much. The main reason many aquarium owners are obsessed about removing algae is aesthetics. 

Here’s a great video that talks more about the good and bad of algae in a fish tank. 

Avoiding Temperature Fluctuations

Once you position the fish tank in its new location, monitor the temperature to determine whether you should be worried about temperature fluctuations.

If there is too much fluctuation, here are some ways to maintain a more consistent temperature:

  • Use an aquarium heater or chiller to maintain the right temperature throughout the year.
  • Add sheers, curtains or blinds to the window to reduce how much heat comes in.
  • Lower the room temperature using AC or a fan.