So what causes the temperature in your aquarium to rise? Well in the warmer times of the year (usually Summer), the ambient temperature will certainly be the main cause. The warmer weather can shoot temperatures up into the 80's or even 90's, and this can be extremely stressful (or deadly) for your reef tank. There are also other factors that contribute heat including pumps, power heads, and lighting.
So what can we do to combat this? Well, there are many angles to try. No one way is necessarily better than the other, and you may wish to combine multiple methods. (Read more after the jump)...
First, let's look at pumps. There are internal pumps (and powerheads) and external pumps. Because pumps have moving parts, they need to cool themselves. Internal pumps cool themselves using the aquarium water that passes through and around them. This transfers a small, but often measurable, amount of heat to the aquarium. Temperatures can vary, but it's not unheard of to hear of 1-3 degree increases from large internal pumps. Adding additional pumps for reactors and water flow in the aquarium can increase this a bit more as well. External pumps sit outside of the water, and often have fans that can cool them or cool passively into the environment. While they often lubricate and cool with water as it passes through, much of the heat is instead released into the surrounding environment, which does not directly affect your tank.
To combat this, we should try to minimize any excess pumps we do not need, and try to purchase energy efficient pumps whenever possible. External pumps can also be a good idea as you can often create a manifold to operate many devices utilizing just one pump.
Lighting is another contributor to heat increases on your aquarium. As lighting trends have changed, they have seemed to grow towards being more energy efficient and cooler running. While explaining the correlation between wattage, radiation, and heat is out of the scope of this article (and my hobbyist knowledge to be completely fair and honest), higher wattage typically means more heat to transfer. T12VHO's, Compact Florescent, and Metal Halides are often the culprits when we discuss heat transfer from lighting. T5's can be cooler, but also transfer a measurable amount of heat. LED's seem to be the current best option in regards to reduction of heat transfer, however proper ventilation (especially when using a canopy) is still necessary. LED lighting is not for everyone, and there is nothing wrong with other types of lighting.
For any heat issue with lighting, I would recommend ensuring that your aquarium is ventilated properly and that fans are utilized in many cases. When discussing lighting alone. fans help remove heat from the lights and pass cool air back over them and the aquarium. They can be installed near the aquarium or into a canopy to help. Another option to consider is to change your lighting cycle. You can have the lights come on earlier or later depending on when temperatures reach their peaks. I tend to have my lights come on in the late afternoon to evening when 1) temperatures are on the drop and 2) I am home to admire my aquarium (that's called a double whammy!).
Next, lets consider ambient temperature of the room. For starters, if you live in a climate where opening a window is possible, do so. If you can leave a door open, do so. Do not shut the aquarium into a room. This is bad for temperature, it is bad for pH. Let it breath! I have had great results leaving the door open to my aquarium room and the window open. I have found that a window fan helps. I use a Walmart-ish fan that sits in the window with two fans that can be controlled by temperature and speed, and also has a temperature control setting; best $29 I've spent! A box fan or any fan you have is also a good option.
If you have air conditioning, this may be an option to consider. It can be difficult (and expensive) to run an air conditioner just for your aquarium, but it may be an option and necessity during peak temperatures. For fish rooms (i know a few fish nerds with these), this may be a good investment.
Another option that goes with the next part (and the lighting part) is to remove the hood. Glass hoods, plastic hoods, and canopies do not allow for good ventilation and can trap heat... Remove the hood whenever possible, and certainly when using a fan (more info below).
Fans for the aquarium can be helpful. "But Chromie, you SAID THAT already!!!" Not exactly... I wanted to give fans a little section of their own (well deserved if I might add). Fans can be strategically positioned to point directly at or across the aquarium water to help cool your aquarium. Fans positioned across the water can help blow heat away from the lights, but more importantly the help increase evaporation. As water evaporates, the temperature can be lowered by as much as 3 degrees (I've heard other estimates). When using this method to help cool your aquarium,you will need to top off your aquarium with fresh RO/DI water frequently; An auto top off system (ATO) is a huge asset for this. You can simply position the fans above the aquarium or wherever there is a large surface area.
The fans can be left on manually, but hooking them up to a temperature controller or an aquarium controller is a nice touch. I use a Walyworld (not an endorsement) clamp on fan connected to my Digital Aquatics Reefkeeper to cool my aquarium. I have the temperature set point a little higher than I expect my aquarium temperature to be, so it kicks on around 80 degrees (i try to keep the aquarium around 78). This has worked well for me in the past when I used T5 lighting, and while I still have the fan set up, it rarely comes on now that I'm using the Maxspect Razor LED system.
This brings us to aquarium chillers. There are many manufactured aquarium chillers on the market. These can be really convenient and easy to use. They are generally not cheap, and can run your electric bill up. Most chillers in the market for aquarium use are rated to be used for tropical temperatures of 74-82 degrees F, with a maximum 10 degree pull down. When selecting a chiller, be sure to size it appropriately! Over sizing a chiller to the next step should be considered if your temperature stays above 82 degrees for a good amount of time (I have heard a benchmark of: Over 82 for more than 72 hours) or if your aquarium volume is near the upper threshold of the chiller's rating.
Below is a general chiller sizing guide for aquarium chillers. This is a GENERAL guideline, and it will vary from one manufacturer to another. Tank min and max are in US Gallons. Disclaimer: Do not use this as gospel, people...
| Chiller Size | Tank Min. | Tank Max |
| 1/15 hp | 15 | 40 |
| 1/10 hp | 20 | 60 |
| 1/5 hp | 55 | 120 |
| 1/4 hp | 120 | 175 |
| 1/3 hp | 150 | 250 |
| 1/2 hp | 250 | 400 |
| 3/4 hp | 300 | 650 |
When purchasing your chiller, be sure to check the rating for HP (horsepower) in relation to your aquarium volume. Account for things such as sumps which can add volume. Due to the large coverage ratings manufacturer's offer for chillers, it is often advisable to move up to the next size should your aquarium run warm often or sits somewhere on the high end of the rating. For example, using the estimated information above, if I was running a 50 gallon aquarium with metal halide lighting and temperature was hovering towards 82 degrees, I would probably go with a 1/5 hp chiller. This would ensure the chiller I buy is appropriately sized for my needs. Technically the 1/10 hp is rated for my theoretical aquarium, however I'm REALLY pushing my luck.
Don't forget, chillers are typically rated for a 10 degree pull down for tropical aquarium temperatures... The ratings you read on the aquarium retailer's website are not rated to chill down to 65 degrees for your Salmon spawning project. Sure, it could probably be done, but don't rely on the ratings listed for aquarium chillers to do this for you (hint: contact the manufacturer). Another thing to consider with chillers is that they need to be given room to breathe, and will perform poorly when over heated. It is not recommended to install a chiller in a stand (unless it is ventilated well), and when the room is super warm, your chiller will not run at peak performance. Think of your refrigerator or car air conditioning; similar principles.
Finally, there is the DIY crowd and options. I'm not inherently against DIY, and encourage it whenever it is a realistic option... but not going to recommend any of these ideas here. Aside from fans, I wouldn't waste my time, or money on any of these options for my aquarium.
I hope these ideas help shed some light on cooling options. Keep your reef healthy, and keep your cool!!! Until next time...
