Beating The Heat – Cooling Your Marine Aquarium In Hot Weather

Welcome to Simple Reefs. We are a brand new website designed to take the stress and expense out of starting your very own marine aquarium. We have been talking about aquarium heaters a lot, as of late. Today we are looking at Beating The Heat – Cooling Your Marine Aquarium In Hot Weather.

After all, it is one thing when your home is cold and you need to warm the water in your marine aquarium up. But what about when your house suddenly shoots up in temperature during the summer? How do you deal with this potentially deadly situation? Well, let’s take a look.

Beating The Heat – A Temperature Crisis in the Home

When I first started this website a few months ago, I didn’t actually think I would be writing this article. It’s not that cooling your marine aquarium isn’t an important part of your ownership journey. It’s just that I had completely forgotten how bad of an issue this can be, even in cooler countries like the UK.

As temperatures rise, many of us will head outside to catch some rays, enjoy the sunshine, and maybe take on some of those car or garden maintenance projects we’d been putting off all winter. Most of us will, pretty rapidly, become accustomed to the increased heat outside and in our homes. Some of us will throw on the AC while others will simply crack a few windows and hope for the best.

While we are leaving unsightly sweat stains all over the furniture, things could be slowly becoming hellish in your marine aquarium. As our houses warm up, so do our aquariums. Perhaps more than you might imagine. I was reminded of this in June of this year when temperatures started to pick up.

All of a sudden, my house was a lot warmer and the lid I had been using all winter was now a big time heat hazard. My aquarium’s temperature was climbing fast, even without the heater running, and the results were quite shocking. A difference of a few degrees between your ambient air temperature and your tank’s water temperature can cause a noticeable increase in just a few hours. But why is that?

Aquariums Can Become Heat Traps

Unlike the vast ocean, the closed environment of an aquarium is highly susceptible to rapid temperature swings. Believe it, or not, the sea is so incredibly enormous that it acts as something of a thermal buffer.

This means that the ambient air temperature in tropical locals won’t impact the sea’s temperature a great deal. There’s simply too much water to heat up to make a big difference. (Of course, climate change is drastically changing sea temperatures but that is a whole different article for a whole different website).

Your aquarium doesn’t have that luxury. It is a closed system and, relatively speaking, is an incredibly small body of water that is incapable of sustaining a stable temperature on its own. If your ambient air cools, your tank water will cool; if your ambient air temperature increases, your aquarium’s water temperature will increase.

This is where things can become seriously uncomfortable for your aquarium’s residents. Most of the fish, inverts, and coral in your tank come from tropical locals with minimal temperature fluctuations throughout the year. They really aren’t adapted to coping with change. Even a small increase of a few degrees can be devastating for your fish, invertebrates, and especially your corals.

The big problem is that your aquarium is, basically, a heat trap. Many aquariums are setup in a way that they simply can’t easily cool down once they warm up. Particularly if the ambient air temperature in the room stays high.

The temperature in your tank will climb to meet the ambient air temperature and then may even keep on increasing thanks to the equipment in your tank. This is where we can really start to see some serious issues.

The Importance of Thermal Stability

Maintaining a stable water temperature is one of the most critical aspects of marine and reef keeping. The ideal temperature range for most marine aquariums is between 76°F and 82°F (24°C-28°C), with stability being more important than achieving an exact number. A sudden spike in temperature can lead to a cascade of, potentially devastating, problems, including:

• Oxygen Depletion: Warm water is capable of holding less dissolved oxygen. As temperature in the water increases, the metabolic rate of your fish and other inhabitants increases, causing them to consume more oxygen. This is a bit of a cascading issue as the increased need for oxygen will deplete the already depleted oxygen levels even further. This can lead to rapid breathing, lethargy, and in severe cases, death.
• Coral Bleaching: High temperatures are a major cause of coral bleaching. We see it the world over with climate change and warming seas and that is the result of only a degree or so increase in temperature. The elevated heat stresses the corals, causing them to expel the symbiotic algae (zooxanthellae) that live in their tissues and provide them with food and the vibrant neon colours that are so desirable in the hobby. Without this algae, the coral turns white and is at risk of starvation.
• Increased Stress and Disease: Temperature stress compromises the immune systems of your tank’s inhabitants, making them more susceptible to parasites and bacterial infections. An increased metabolic rate can have massive consequences for both fish and coral.
• Algae Blooms: Warmer water can also encourage the growth of unwanted algae and heterotrophic bacteria, leading to cloudy water, nutrient spikes, and poor water quality.

While we can easily warm up our water using a marine aquarium heater when the temperatures in our homes start to get a bit chilly. What can we do to cool our aquariums when the mercury climbs? It’s not as if we can purchase coolers for our aquariums, right?

Well, believe it or not, we actually can purchase coolers for our aquariums. They should, really, be a bit of a last ditch resort, though. Fortunately, there are several strategies, from simple and inexpensive to more advanced, that can help you keep your marine aquarium cool and stable during a heatwave. Let’s take a look.

Passive Cooling Methods – Affordable Solutions

These are your first line of defence against aquarium temperature increases and are great for minor fluctuations. For most setups and in all but the hottest of countries, these methods should suffice to help you avoid a heating catastrophe.

They focus on reducing the amount of heating being introduced to your tank and using natural, tried and tested, processes to cool the water. Start from the first suggestions and work your way down until you start to see temperatures settle down a little.

• Remove the Cover or Use Mesh: This was, literally, all I needed to do to see my aquarium’s temperatures drop down to a normal level. I have a sealed lid for winter to keep the heat in and a mesh lid for summer to stop my fish from taking a Fosbury Flop out of the tank. I simply switched back to the mesh lid.
  
  A sealed aquarium lid or hood traps heat and moisture. One of the ways your tank will lose heat is through evaporative cooling. This can only happen if the water can actually escape the tank. Removing any covers or replacing them with a mesh screen top will allow for better air circulation and evaporative cooling will begin to take place.
  
  
• Shade the Tank:This one is quite simple, if your tank is in the view of a window or hit by direct sunlight, find a way to shade it. You can do this with some simple blinds to change the direction of the light or, more drastically, cover the tank with some cardboard. You could even get creative and fashion a purpose made shade to make sure your tank is not being warmed by the sun.
  
  
• Agitate That Surface Water: Now I don’t mean to tell it all about your day and how difficult your life is. I mean agitate the surface water – get it moving around. You can do this with a wave maker pointed at the surface or even a fan running over the surface of the water. This will get things fizzing up a bit and allow for more gas exchange which will, in turn, reduce your aquarium’s temperature through evaporative cooling.
  
  
• Grab a Specialised Aquarium Cooling Fan: This is one of the most effective and affordable cooling methods and it goes back to evaporative cooling. Much like the suggestion above, these specialised fans clip onto the rim of your aquarium and, basically, accelerate the rate at which the water evaporates from your tank.
  
  Now this will mean that you need to top up more. Remember to keep an eye on your salinity, that’s very important. But for around £15 you can really increase the amount of heat that is leaving your tank and drop your tank temperatures effortlessly.
  
  
• Turn Off or Reduce Lights: High-intensity lights, especially older Metal Halide fixtures, are a major source of heat. I mean, just put your hands in the vicinity of them to see that. Notice how your LED lights typically have metal grills on them? Those are heat sinks to reduce the build up of heat and allow it to escape. The closer your lights are to your aquarium, the more heat they will be producing in your water.
  
  Reduce your lighting schedule during the hottest parts of the day or, if your setup allows, turn off the lights entirely for a day or two. LEDs are generally cooler but still produce some heat. Consider running your lights during cooler hours only, such as early morning or late evening. You may just be surprised at the difference it makes.
  
  
• Try To Prevent Your Room Warming Up: This tip is pretty simple but, potentially, not very practical. Attempt to prevent your room containing the aquarium from warming up in the first place. Keep blinds and curtains shut, keep air circulating, and open windows during the night time to cool things down a bit.
  
  
• Move the Tank: This is the most drastic solution and may not even be a consideration with larger tanks. With smaller tanks, however, you should seriously think about relocating your aquarium. After all, this will happen year upon year. If possible, relocate your aquarium away from direct sunlight and heat sources like windows, heaters, and vents.
  

Those are some of the simple and affordable ways to beat the heat and cool your marine aquarium. But what happens when you are in an absolute emergency and have no time to allow those changes to kick in? You are going to need to get creative and opt for some drastic solutions.

2. Emergency and Temporary Solutions

When temperatures are spiking rapidly, these methods can provide a quick, temporary fix.

• Float a Frozen Water Bottle: Anyone who has owned mammals that are struggling on a hot day will know about placing a frozen bottle of water into a towel to cool the animal down. It can work for marine aquariums too but in a slightly different way. A very simple and effective trick is to fill a clean plastic bottle with RO/DI water, freeze it, and then float it in your sump or display tank.
  
  The ice will slowly melt, gradually cooling the water but, crucially, without causing a sudden temperature drop that might shock your residents. You can use several bottles in a rotation to maintain a consistent cooling effect. This technique is adaptable to a bunch of different situations.
  
  
• Use a Bag of Ice: If the frozen bottle isn’t cutting it, you may need to take more drastic action. Similar to the frozen bottle, you can place a sealed bag of ice (made from RO/DI water) in your sump. This is a last-resort option and should be done with caution to avoid a rapid temperature drop. The added volume of ice will cool the tank rapidly. Be cautious of the water overflowing, as well.
  
  
• Perform Small, Cooler Water Changes: Again, this is a bit drastic and may not be all that simple to accomplish on short notice as salt does not like to mix well in cool water. With that being said, a partial water change with water that is a few degrees cooler than your tank’s temperature can help bring the overall temperature down. Be careful not to make the new water too cold, as a sudden change can shock your livestock. It has to be gradual and small.
  

These are temporary and quick-fix solutions. If you need to employ these on a regular basis and the tips in the passive cooling section don’t help. You really need to, potentially, look at a more long term and more active solution like the ones suggested below.

3. Long-Term and Active Solutions

For serious reef keepers or those in consistently warm climates, active cooling is the best way to ensure temperature stability. The solutions below should, obviously, be employed with an aquarium heater to maintain stability. Take a look at our article on why it is important to still use a marine aquarium heater in warm houses and climates for more information on why.

• Insulate Your Aquarium: This is a bit of a drastic option but can definitely help with both heating and cooling. Placing some type of insulating material around the sides and back of your tank can help prevent the tank warming or cooling too much. You should always employ this method with other passive cooling methods or you may just end up trapping heat in. It is worth considering the aesthetics, as well, as this will look quite ugly in many setups.
  
  
• Install an Aquarium Chiller: This is the most reliable and efficient method for cooling a marine aquarium but it also the most expensive. An aquarium chiller is, basically, a refrigerated unit that works like an air conditioner for your tank. Water is pumped from the aquarium through the chiller, cooled to a precise temperature, and then returned to the tank.
  
  Aquarium chillers are typically connected to a temperature controller that turns the unit on and off as needed to maintain a set temperature. While chillers are a significant investment, they offer peace of mind and are essential for protecting expensive and sensitive corals in very warm climates. Keep in mind that they are an added point of failure so will need to be accompanied by close water temperature monitoring.
  
  
• Air Condition the Room: For smaller tanks or those in a single room, a room-based air conditioning unit can be a very effective way to keep the entire environment cool, which in turn cools the tank. Again, monitor temperatures closely and keep your marine aquarium heater on at all times. Even homes with AC experience fluctuations of temperature.
  

The Importance of Monitoring

No matter what cooling methods you use, consistent monitoring is key. Invest in a reliable digital aquarium thermometer. You can purchase examples that feature probes meaning they can be left in the tank at all times.. Placing the thermometer probe in a high-flow area of the tank, away from heaters or chillers, will give you the most accurate reading of the overall water temperature.

By doing this, you will never be guessing your aquarium’s temperature and you will be ready for any swings. By being proactive and having a plan in place, you can ensure that your marine aquarium remains a stable and healthy environment, no matter how high the mercury climbs. Thanks for reading and spending your time at Simple Reefs.