For those of us living in 30°C (86°F) climates. Having a fan blow gently across the top of the tank can potentially lower temperatures by 1-2°C. For a more detailed explanation on why this is so, you might want to do a search on "Latent heat of evaporation". The fan also serves to move the heated air under your lights, so you get to kill two birds with one stone.

This mod is also excellent for those with an enclosed hood and want to exhaust the hot air out. Simply cut a few holes in the hood with a hole saw and mount the fans. You can also do a intake-exhaust configuration.

So let's get on with it! All you need is some spare pc fans and something to power them with.

 

PC Fans

I'm sure many of us will have easy access to these fans. The most common ones are 80mm, 92mm and 120mm. Airflow (CFM) and noise (dBA) vary among manufacturers, so you'll have to choose the right ones to use. You won't need to have a hurricane blowing over your tank. Too much airflow and you'll find your water evaporating too quickly. The extra agitation of the water surface might also cause some CO2 loss. A gentle breeze is best.

Here are some quick hints to keep in mind when choosing fans. Bigger fans can potentially be quieter and still move a reasonable amount of air when run at lower speeds (more on that later). You'll want to have fans that are at least 80mm. Then, if you have the fan specs, look closely at that. Most fan manufacturers will have the specs listed in their website. Typical specs listed will include voltage, rpm, CFM and dBA. Voltage rated is usually 12V. You'll want the best combination of high CFM with low dBA. This will give you a strong quiet fan.

 

Fan Mounting

Any secure method of mounting will do, as long as the fan doesn't drop into your tank and short circuit. Below are a couple examples.

Here I simply zip-tied them to the support legs for the lights.

 

Here's a similar mounting with spare legs.

 

This is more elaborate. I cut some acrylic to size, heated it up to form the bend and attached it with a U-shaped strip. Yikes! Lots of dust!

 

I find that using a slight angle works best. This will blow on the water as well as move the heated air under your lights. Direct the fan so that it blows across the water surface. This will cause very slight ripples (great for Amano-style pics).

 

Power Supply

Moving on to power. For the purpose of this article, I will only discuss using computer parts to manufacture a cooling solution for the tank. There are several ways to power a PC fan. You can certainly use an adaptor if you have one on hand. An adaptor is good for a fixed amount of power draw. You can gauge that by looking at the sticker on your adaptor (also on the fan) and calculating how many fans it can support. Be careful not to overload the adaptor as that can lead to overheating and possibly electrical fires! As I had several tanks in close proximity, I opted for using a computer power supply unit (PSU).

The good thing about using a PSU is that I can add/reduce the number of fans as I please without any risk to my health or property. A PSU is more flexible as it will only draw as much or as little power as needed (depending on the efficiency). Since we're only dealing with fans, you don't really need a 600W monster PSU. Just any low powered one will do nicely.

Now if you skipped reading this part and hooked everything up, you'll realize that it doesn't work! A PSU cannot be powered on without a motherboard, or can it? Depending on whether you have an AT or ATX PSU, you'll need to perform this next step so that you can run the PSU without your motherboard.

Here's a pic of the simple bypass. For more details, do a search on "powering a PSU without motherboard".

 

Now let's hook it all up! Place the PSU in a nice dry area and make sure everything is well grounded. Check your water temperature. It will drop after 2-3 hours.

 

 

Fine Tuning & Maintenance

If everything's running just the way you want, then you're all set! However, there'll be situations where the fan you have might be too powerful and/or noisy. I had some 120mm fans that were so loud I swear my fish couldn't sleep well. Undervolting the fans will cause them to run slower and quieter. Seeing that their original specs had seriously high CFM, I undervolted them to 6V and still had enough airflow.

You can undervolt fans to 5V, 6V and 7V through simple re-wiring. Another option is to use a Fan Controller. I usually have 2 fans per tank, so I undervolt them to 6V by re-wiring them to run in series. You can use an internet search for more details on the other alternatives. (Just a quick note that not all fans will power up at 5V.)

Maintenance? Almost none! All you have to do is to clean the fans every couple months. As you've noticed from some of my pics, dust will accumulate on the fan blades and around the mounting. I use a paint brush and vacuum cleaner for a quick spot cleaning. Remember to switch them off first! You don't want to lose a finger.

All done! Now my fans are quiet, my tanks are cool, and my fish can finally get some shut eye.

 

 

 

Back to Top