This seems to be one of the more popular pages on my site, so I figured it was time for a refresh of the content. Over the years I have moved away from internal fans, and moved to active but tuned air ventilation in stock Exoterra and Zoomed terrariums. I’ve found I can maintain more realistic vivarium temperature and humidity values by using low speed silent exhaust fans to both cool lighting fixtures and draw air through the vivarium using variable sized upper vents.

I have maintained the information on the circulation fan designs I have used in the past at the bottom of this page for those of you interested in replicating the magnetic mount and camouflaged fan designs. Air circulation can aid in clearing the vivarium glass for better viewing and it may also be beneficial to certain plants.

Venting a custom vivarium hood

This was the first custom vivarium hood that I made that leveraged a blow hole for active hood and vivarium venting. The hood has weatherstripping running the perimeter of the top to create a tight seal with the vivarium. This allows for air to be drawn through the vivarium starting under the door on the stock vivarium vent, moving up the front glass and out the custom top vent that runs along the front of the viv. This air is then exhausted from the hood, thus circulating air through the vivarium while cooling the LED lighting that is installed within the hood. A piece of cut glass was used to manage the vent width, allowing me to control the airflow through the viv while maintaining adequate cooling of the light fixtures.

Here are a series of images of the installation:

Fan mount	Front vent	Blow hole fan grille

Low profile hood	installed blow hole	installed lighting

I have now used this design on 4 18x18x24 vivariums and I will continue to use it for all new vivariums. The main modification that I have made over the years was to reduce the number of LED lamps from 3 to 2. I found the frogs preferred the more subdued lighting conditions and the third lamp was not needed.

Vented vivarium hood construction

Here’s a pictographic log of the construction of the vented hood presented above.

Testing vivarium active venting

The following section presents a series of 24 hour tests that used a variety of fan speeds and data recorder locations. The purpose of this testing was to determine the optimal fan configuration that would maintain the proper vivarium conditions before placing animals in the vivarium. Click on each image for a full size view of the graphic. A description of the experimental conditions is presented to the left of the plot. Each plot contains the following elements:

The horizontal axis is time in hours.
The vertical axis is temperature in Fahrenheit.
The black dotted line is ambient room temperature recorded by an external data recorder.
The white line in between the tan and gray shaded regions is the average temperature for that hour.
The tan lower shaded area is the lower 95th percentile confidence interval.
The gray upper shaded area is the upper 95th percentile confidence interval.
The lower bar plot represents the delta between the average vivarium temperature and the average ambient temperature.

Test 1: upper shelf temp, low fan / low controller speed

Test 2: upper shelf temp, medium fan / low controller speed

Test 3: upper shelf temp, high fan / low controller speed

Test 4: upper shelf temp, high fan / high controller speed

Test 5: vivarium floor temp, high fan / medium controller speed

Test 6: upper shelf temp, high fan / medium controller speed

Test 7: upper shelf temp, high fan / low controller speed

Test 8: upper shelf temp, high fan / medium controller speed

Long term vivarium temperature and humidity monitoring

The venting system has worked quite well, stabilizing the temperature and humidity data that I have been monitoring during the vivarium standup process:

Camouflaged magnetic mount blower

So can you find the fan in this vivarium:

This was a fun project! There is a blower embedded in cork bark and sphagnum moss. I also used stainless steel screening to close up the intake and exhausts. Here is the process I followed:

blower unit (60mm)	intake	outlet	power

embedded magnets	embedded magnets	magnet mount	installed fan

front view	wider angle…	wider…	full tank shot

This ended up being the second generation magnetic mount fan design I implemented. I wanted to hide the fan from view so I glued cork bark and sphagnum moss to the blower.

Magnetic mount fans

This was my first set of circulation fans. They used magnets siliconed to the top of the fan. I used fiberglass screen to keep toe pads out of the fan, and then added a fan guard on the outside of the fans for added protection. They were good circulation fans, but in the end I did not necessarily like the look of them suspended in the viv in plain view. Here is a build sequence:

magnets	magnets siliconed	close up	paired magnets

60 mm fan	60 mm mounted	60 mm wired	stacked magnets

Venting a standard Exoterra hood

I’ve used Exoterra hoods on two of my vivariums. Each vivarium has a pair of hoods. I used directional JungleDawn LED lights that allowed me to remove the stock reflectors from the hoods and replace them with 80mm PC fans that exhausted air from the hoods. I had to drill holes for the screw mounts and clear out excess plastic to allow for a tight fan fit. The following images illustrate the process and show the installed fans: