Understanding Air Movement
Alright, so I went over this in a google document prior that I shared with people in the Tarantula Addicts discord. By the way you can find me there under the screen name Lunarae. Anyways here is a revisit to this topic with a little more to the subject and why it's so important. I wanted to add quick links for you guys but it wont let me put anchors within the blog posts, at least not in a way I have found so far, if anyone knows how to do this with wix blog posts please let me know.
Why does it matter?
First lets understand why air movement in an enclosure is important. Of course the first aspect of this is that we want there to always be a fresh supply of oxygen for our animals, it's why we make sure air can pass through in some form or fashion. Without a fresh supply of oxygen our animals would die, contrary to what some may think, this is necessary for inverts as well.
However just being able to have oxygen isn't exactly enough, there needs to be a level of air movement or air flow to produce a healthy environment. Without good ventilation you can end up with moisture build up inside even a dry enclosure because it cannot escape properly when temperature changes occur. When this happens you're humidity will rise inside the enclosure, with higher humidity levels stagnant air becomes a bigger problem, with stagnant air comes the ability for various non-beneficial bacteria to grow, this in turn can produce mold and fungus you don't want in your enclosure.
Not only does this make it easier for non-beneficial bacteria, mold, and fungus to grow, it can also be very hard on the animals if they are not biologically built to breath in high humid environments. In fact even species from environments with high humidity like C. versicolor do not do well in high humid enclosures that lack air movement and will die. Many new keepers to the hobby have tried to keep these beautiful species only to have them die on them quickly because they kept the enclosure at humid levels the species was from but did not have adequate air flow.
The way I try and help myself understand it, is that by having to much humidity in the air, and not enough fresh air coming in, it's like the animal is slowly drowning for all the moisture it's taking in instead of fresh oxygen. Whether that's exactly what is happening or not, I don't know. But my logical mind set sees it as that's the case, and is why having good solid airflow is so important for any enclosure you keep animals in. Even the dry climate enclosures need to have plenty of room for air to pass through.
How does air flow work?
OK so you understand now why it's important. How do we make sure we provide our animals with good air flow? How do we know if we're doing it right? Well first there's some basic principles in how air functions that we need to understand.
Some of us learned this in high school, others may have not learned it yet, or some of us went to a school where they didn't actually touch on this subject to much in their classes. Whatever the case is, if you follow the link Here. You will be directed to High School Earth Science/Air Movement from WikiBooks. This explains the basic's on how hot and cold air create different pressures and how those pressures create air movement.
If you didn't click that link and you are not familiar with how hot and cold air creates currents, I advice you now to go and click it. It'll open up in a new tab so you wont lose your place here. It's educational and more applicable in understanding the weather, though of course some of the principles it discusses apply's to what we are talking about here.
Understand that humidity and air flow can go hand in hand and it's a very delicate balance that requires attention to detail to really achieve this. By understanding that hot air rises and cool air sinks we can utilize that to our advantage by how we place our ventilation in our enclosures so that we ensure the entire enclosure gets good air flow and creates the best air environment for our animals.
So lets look at the first picture I have here. This picture was found through a google search and it's source is an article going over how to place windows in a house to increase air flow. Another interesting read so if you click the picture it will link you there. But this diagram is a good example of setting up an enclosure for good air flow.
Now looking at that what you are seeing is the concept that as the hot air rises, it pulls in the cool air from the lower vents. Where we have vents places on the enclosure helps control how the air flow moves through the enclosure as temperatures change causing air pressure changes, and from there air movement.
Now an enclosure is a much smaller scale then that of a house. So you're not going to create a wind current you could feel by any means. However it's important to know that utilizing the various air pressures like in the diagram above is important to help keep air fresh and clean.
Of course though the method above is not the only one out there, it is one that focuses on using air pressures to move the air and isn't reliant on wind movement to circulate air. So keep that in mind, the above does not have to have a wind source in order for that process to take place. Leaving it at that can be all that is needed for a dry climate enclosure.
However, if you were to go with something that has higher humidity levels you would want to utilize a fan to help the air move through at a faster rate to compensate for the humidity levels. But with this you end up losing humidity faster and having to experiment a little to create the proper balance so you have enough air flow but keep humidity levels where you want them. When people delve into setups like this, usually it's with a bio-active set up and they will have various gauges to help them figure out humidity and temperature levels.
If you are like a good majority of keepers out there, the appeal to keeping inverts is the fact that all that fancy stuff isn't exactly required or needed to provide a good environment. While I myself am interested in bio-active setups and natural looking vivariums that's a personal choice and passion I have. It of course doesn't mean that's how everyone else has to do it, which is why I'm going into detail here about Cross Ventilation.
Now Cross Ventilation is another form of air movement and control and it's the most popular means that most invert keepers use for their enclosures. Unfortunately though, I have noticed that a lot of people don't understand what Cross Ventilation is, and that's due to the name itself.
Logically one assumes Cross Ventilation means going through one side and coming out the other side directly across. It's easy to think that's the ONLY concept of Cross Ventilation, however it's not. In fact some forms of Cross Ventilation utilizes the principle I showed above. All Cross Ventilation is, is the concept of placing ventilation openings to optimize air flow utilizing already occurring natural breezes outside of the enclosed space. So lets stop some of those arguments people keep having over only air passing through one side of an enclosure, cause lets look down at the diagram below.
Now this image I got off of a google search as well, but I'm not entirely sure where it's original source is from. If you know, let me know so I can link the picture properly and give them the credit they deserve.
Though take note to what it says there, and the different forms that they have there too. These work by utilizing the natural breezes, and some work better because they also utilize the air pressure we discussed above. However for these to function properly you have to have some sort of air movement in the room that the enclosure is in. Be it a fan on the ceiling, a fan set up somewhere in the room pointing towards you're enclosures, a fan attached to an enclosure for a more direct approach (People have used pc fans for this to provide a more direct approach without creating to strong of a breeze). Or some people are lucky enough to have pushed air and heat installed in their homes to help circulate air. Depending on your situation, you have to decide which method is the one for you.
To note, because it's asked a lot, in terms of using aquariums for enclosures this is perfectly acceptable. As long as you provide plenty of ventilation in the top for air to pass down and up it can create it's own natural air cycle where hot air pushes up one side, and helps pull cooler air through the other vent. (Again, that first link I gave you, if you didn't check it out I advise you do, they have diagrams that explain that cycle). Much like the diagram above where one side only has two holes opened. When dealing with dry climate enclosures as long as you have plenty of ventilation for air to pass through you don't have to worry at all. More humid enclosures you are looking at needing to provide a little extra air flow utilizing a fan to help it from becoming stagnant a little better. And in these cases using the fan (Talking about a pc fan) to blow air OUT of the enclosure is what helps better and helps hold humidity better then blowing air IN. Least from what I've read thus far. When I start down that road I'll be sure to write more in depth on the topic of fans.
So what's the best way to do a Terrestrial Enclosure?
Alright, we get the basics now, why it's important and how it works. So lets apply that to making a Terrestrial Enclosure. Most people are inclined to get Tupperware or some form of acrylic box like structure with a lid to provide housing for their inverts. This is perfectly acceptable. Just keep in mind what we just discussed when placing your ventilation holes.
For terrestrial enclosures where you are capable of providing air vents on the sides of the enclosure AND top, I recommend holes that run right along the top of where the substrate meets. So basically ground level for your tarantula, or other invert. Of course you make sure these are as big as you can get away with, without them managing to escape. Depending on how big you can make the holes determines how many you actually will need. If you have to stick with very small needle sized holes, be aware you're going to want a lot of them so you have a good circulation of air. A way to measure how big to have the holes is by noting the size of the carapace (head) of the tarantula, as long as the holes are not bigger then that, the tarantula will not be able to escape.
Now I would say to place holes along the ground level, along the top edge of the opposite sides of the enclosure, and then the center of the top of the enclosure. So basically mimicking the first diagram shown. But here's another one that I made to show what I'm talking about.
If you cannot provide air vents at the top of the enclosure, and can only provide them in the sides. Then I would in that case focus your air vents towards the center of the side of the enclosure. I would not suggest a row along the bottom, and a row along the top in this case because what you will end up doing is creating air flow just along the walls of you're enclosure, but not towards the center area. Basically your fresh air current will ride along the wall of the enclosure because of how hot and cold air pressures work, and while this can work fine for smaller enclosures, larger ones with more space in the center will not benefit from this as shown in Image A. Which is why a set up like image B is better for those where tops can't help vent out air.
When aquariums are used for terrestrial set ups, what I recommend then is to have a set of holes on either side of the top lid of the enclosure. Depending on how big of an enclosure you have, you may need to do large sections of holes. The first idea that may come to mind to provide enough air flow with these would be a mesh screen top, if you have inverts that cannot climb glass this can work perfectly fine and provide plenty of air flow. However if you are using it for tarantulas, who can manage to get up to the screen lid, this is ill advised. They have tarsal claws that can get caught in the screen mesh, and when they lose their grip, end up dangling from the top unable to save themselves. This tends to result in loss of limbs for the Tarantula. So it's suggested to make acrylic lids with ventilation holes to provide a safer climbing surface for your tarantula.
Now the three small tanks to the right are two and a half gallon tanks. With these, the only moisture I provide is the water that goes into their water bowls. I don't water the substrate at all, so I have plenty of air flow to keep up with the humidity caused from the water bowls. If I was to moisten the substrate often, I might want to consider larger holes or more of them to compensate, maybe even a fan. However these guys like it dryer so it works well.
The picture to the left is a twenty gallon tank that I actually do keep moist, as you can see I have some live plants which are thriving really well, I have some moss in there too. I have compensated with the added moisture needed by the plants, by having plenty of air holes at the top, as well as separating the lid into two parts. I will admit now, I need to make a new lid, it bows easily and I have to flip them both each day. I'm not concerned for an escape though because inside is our LP and she really doesn't seem to like climbing up on the glass, she had a hard time holding on so seems to avoid it. However it is something I need to fix because it isn't very secure and she could always get a wild hair and go against her usual behavior. I'm looking into using egg crates (The ceiling light stuff people use to make false bottoms in some vivarium setups.) as a possible alternative to a safer lid. I'll update you guys on that and if it works well or not when I get around to it.
Something else to note just because of the picture for my LP's home, when you look at it you can see there is a lot of space from the substrate to the top of the enclosure, for terrestrials it's not advised to have so much space there. It's better to not exceed 1.5x the diagonal leg span of the tarantula in terms of height, because terrestrials do not grip well when climbing and could fall. A tarantula with a large abdomen suffering from a fall could split their abdomen or end up with internal bleeding and die. My set up is the way it is because our LP isn't keen on climbing the glass because she does not grip well, it doesn't mean the danger doesn't exist still technically exist. That is a personal choice I made. I just want people to be aware when viewing that picture it's isn't common practice to have that much space there.
Anyways, these are the basic methods I would focus on in terms of ventilation for enclosures, this isn't going into anything else, just focusing on proper air flow and making sure there is enough for you're animals.
So what's the best way to do an Arboreal Enclosure?
I saved this for last which some people may actually find frustrating because Arboreal tarantulas are the ones where ventilation is the most important. They need it more so then terrestrials because they are used to being up where there is a lot of air flow. Terrestrials like to be down in burrows in the ground where air flow doesn't occur as often, where as arboreal animals deal with life up in the trees where they can deal with breezes creatures on ground level never deal with.
Here it's really the same as with terrestrials honestly. Same concepts and fundamental guidelines apply. However because we generally deal with less substrate and more open air, and arboreal tarantulas tend to make their dens along the tops of the enclosures, it can dictate how we decide to set these up.
While I do believe having ventilation along the bottom and top sides of the enclosures then the top part of the enclosure is one of the best methods, with some tarantulas this can prove difficult because they will web up over the ventilation holes along the top, cutting off air flow and causing issues as shown in Image A above.
Knowing what type of arboreal you have and their behaviors will allow you to know if this is a good set up to use. For instance, I might not suggest this for C. versicolor because they tend to like to do a lot of webbing along the top and if the enclosure is small they may web up the entire top area. But for something like P. metallica this set up would probably be fine. Of course it is also dependent on how you set up the inside of the enclosure to how they may decide to have their burrow as well.
You can also use a set up like some of the more popular exoterra tall
enclosures where it has ventilation along the front below the door, and then it has a screen top. Letting air be pulled in from the lower front and pulled up out the top. This is perfectly acceptable too, and again having air flow in the room really helps with set ups like these. I would recommend though in these setups to replace the mesh screen with acrylic and make sure that the holes you put in are either all the way across, centered, or more towards the back of the enclosure instead of closer to the door, just so that air current really moves through the whole tank. Don't follow my example here where I put the holes along the front by the doors, I wasn't well versed in air ventilation when I did this and so I need to redo the top. When I do redo it I'll show how I went about it.
If you decide to go with another common method people have done, and put an aquarium on it's side, with ventilation coming through an acrylic or Plexiglas door that you've made, this can work as well. Keeping ventilation along the bottom and top of the door. I have to stress however with this method you really will benefit from having very good air flow in the room to help push that air back. Otherwise you'll have a similar issue as brought up prior where air only comes in the bottom, rides along the door and out the other side. People use this and it can work fine, but make sure you have a fan in the room at the very least when doing this to help ensure that air gets pushed further back into your enclosures before coming out the top.
What other ways are there?
Well that's the beauty of DIY, and of educating yourself on the principles of air movement. Once you understand how that works and functions, it leaves you open to try all sorts of ways to go about setting up you're enclosures. You can get as creative as you want and if you're really inventive you can turn almost anything into an enclosure for you're inverts. Saving money and possibly providing some really cool decorative pieces in your home.
I hope you found this article useful. Feel free to tell me what you think by sending me an email, or you can find me on discord. Either way, thanks for reading. As a side note I'm not sure if I will have an article out next Friday. My hubby will be coming home and I like to spend as much time focused on him as I can when he is home, so if I don't get one out that's why. Regardless I'll be sure I get one out by the first of September though if nothing else!
