CO2 Dangers in non-vented Vivaria

[Philsuma]

CO2 Dangers in Vivaria
Thomas Falk Swedish Dendrobates Society

This article first appeared in Tilgiftaren' the newsletter of the Swedish Dendrobates Society. We wish to thank Lars Österdahl for translating it from Swedish.

Preparing for a short field trip I wanted to make sure that my four newly metamorphosed E. tricolor would have constant access to food during my absence. It seemed a good idea to move them to an old 30 litre aquarium that contained a layer of old oak and beech leaves in varying degrees of decomposition that was being used as culture of soil invertebrates like springtails and small woodlice. The resident fauna was supplemented with a fair number of vitamin dusted small fruit flies.


Aquarium type
Returning from the trip I found a froglet sitting on the glass wall, and as there seemed to be a lot of fruit flies left, I did not rush to return the frogs to their normal terrarium. To my dismay, when I decided to do so a few days later, I found the second froglet on the soil surface in a cramped position with its hind legs stretched and the front part of the body raised on the front legs. A little deeper in the leaf layer a dead froglet was found in about the same position, hind legs stretched and head bent upwards. The fourth frog was nowhere to be found and it had probably entered the food chain of the soil fauna.
The two still living young were quickly moved to a 'hospital tank' with wet moss. The larger of the two, the one I had found sitting on the glass, quickly recovered and ate flies the same day. The smaller regained some mobility in its hind legs in the next 24 hours, but it had recurrences of jerks of the hind legs, and I never saw it eat. It died after another two days. The surviving frog was kept under observation foursome weeks until it was returned to the original terrarium, where it developed normally.

Terrarium type
Had the frogs been struck by some kind of infection, or could it be that the frogs had become victims of some poisoning? I realized that I had not modified the aquarium in the same way as my frog terraria. This one had no vent openings close to the bottom. I began to suspect that the frogs had become victims of carbon dioxide poisoning.

Carbon dioxide a threat
Carbon dioxide (CO2) is an odourless gas that normally makes up 0.04% vol. of the atmosphere. In mammals expired air normally contains 4% CO2 as a result of metabolism. An increased level of CO2 in the air makes it more difficult for the body to get rid of this waste product, and the body reacts with increased breathing activity. If the carbon dioxide cannot be removed from the blood a lower pH results, which seriously affects the salt balance, a state called "acidosis". Breathing in a CO2 level of about 5% leads to unconsciousness in a human and higher levels can be lethal.
The sensitivity to levels of the gas varies between organisms. Animals living in the soil or among fermenting material have the highest tolerances. One soil living species of springtail can survive in up to 35% whereas another, living in the vegetation does not tolerate more than 2%. It results from the decomposition of leaf litter, from fermentation, and from respiration.
Carbon dioxide is over 60% heavier than air. In a vivarium with insignificant air movement CO2 will accumulate in the lower parts and a gradient results with the higher concentration at the bottom. If the terrarium has no opening at a low level a death trap may result. Other possible waste gases in a terrarium, like methane or ammonia are much lighter than air, and thus easier to vent away.

Drainage of heavy gas
CO2 ExperimentIn order to test the CO2 hypothesis I got three one-week-old E. tricolor froglets from a friend. They were placed in a small bottle with an inlet hole under the bottom material (Leca; peat moss; leaves). A fine meshed screen covered the upper opening. The frogs soon found their favourite places where they sat after feasting on the fruitflies that had also been introduced.
When I saw that everything looked normal I let CO2 enter the bottle through the inlet. After a few minutes the frogs began showing signs of restlessness, jumping around in an aimless manner. After another minute the first signs of cramps began to show, and two of the small frogs fell on their backs. Soon all three lay motionless with their hind legs outstretched and no visible breathing movements under their chins. To prevent certain death I ended the CO2 influx and ventilated the bottle. No visible improvement occurred until after about 5 minutes oxygen enriched air was blown into the bottle. Since no breathing was present, any gaseous exchange had to take place entirely through the skin.
The first signs of life were seen after about 15 minutes and after another 5 minutes all three frogs were sitting upright, breathing normally. A few hours after the experiment they were all feeding, and with no lasting symptoms.


Experiment with low Oxygen
Since the production of CO2 is often connected with the consumption of oxygen it is possible that the result of this experiment was due to low oxygen rather than high carbon dioxide. For this reason a second experiment was performed with the same set up and the same frogs. This time argon gas was used instead of carbon dioxide. Argon is an inert, non-poisonous and odourless, non-combustible gas. As the oxygen inside the bottle disappeared, the frogs moved around in a much calmer way than in the CO2 experiment. After a few minutes they opened their mouths in a strange way, as though yawning. No cramps were observed, but they sat shrunken. After another minute the breathing movements ceased and they no longer reacted to touch. The experiment was terminated, and oxygen-saturated air was blown into the chamber. After five minutes all three frogs had recovered.
Interpretation
In order to reduce the stress and avoid unnecessary harm to the frogs, the two experiments were performed more rapidly than would be the case under natural conditions. The experiments show that an increased level of CO2 causes unrest and cramps, whereas the low oxygen situation is characterized by a languid attitude without unrest or cramps. Therefore it must be assumed that the death of the three original tricolor was not a result of a too low oxygen level.

Air movement when lid is opened
Simple calculation shows that in a closed compartment the CO2 level can reach lethal levels long before the oxygen level gets too low. Therefore oxygen depletion is no real risk in a transportation box or a terrarium.
The experiments have strengthened my assumption that the frogs died from CO2 that had accumulated near the bottom of the tank, with a number of other factors playing a part:
1. The lid lay on glass flanges that were meant to keep springtails etc. in. The only ventilation was a small gauze type net in the cover, which made air movement difficult.
2. The lighting was a 5W compact fluorescent lamp placed above the cover glass. This gave minimal convection inside the tank.
3. Only a small plant was present in the tank and in the lowlight it had little chance of absorbing a significant amount of carbon dioxide.
4. The leaf litter was "ripe" and the population of soil invertebrates considerable.
5. Small pieces of banana were fermenting, thus producing CO2 (and alcohol).
6. The tank was left almost a week without the usual daily opening of the cover. This provided ample time for the heavy carbon dioxide to accumulate at the bottom.
How common are CO2 problems?
The loss of my E. tricolor froglets is probably not a unique event in the hobby. One hears reports of 'unexplained' deaths in cases where old aquaria, plastic containers etc have been used for temporary holding frogs, for instance in quarantine practice or directly after metamorphosis which means when the frogs are extra sensitive to stress. As long as the cover is lifted every day for the input of fruitflies, the build-up of stagnant CO2 rich air at the bottom is made impossible. When the terrarium is left unattended for a few days, perhaps with extra fly bottle inside to provide food in the unattended period, the combined effect of the extra fermentation and the poor ventilation can be fatal. Deaths among a group of froglets or a quarantine tank tend to be blamed on infections or parasites, but the real culprit may well be an unsuitable tank.

[dtfleming]

Interesting

[Philsuma]

I can personally attest to this as being more commonly occurring in our hobby than most people believe.

Coupled with high heat or heat thrown off from lighting ect = absolutely deadly.

[frogfreak]

We lost a pair Matella Crocea this way. At least we think that's what happened. The one and only time we used a 190oz container.

We went away for 4 days and came home to dead frogs. The rest of the collection was fine...

Thanks for posting this, Phil.

[Philsuma]

This is gonna sound silly, perhaps....but....

I tend to blow into the vivs when I open them to feed, water ect.

This causes the plant leaves to move, shakes up the exisiting, uneaten fruit flies and also helps to dissipate any low lying CO2.

[frogfreak]

This is gonna sound silly, perhaps....but....

I tend to blow into the vivs when I open them to feed, water ect.

This causes the plant leaves to move, shakes up the exisiting, uneaten fruit flies and also helps to dissipate any low lying CO2.

Funny, I do the same thing with the froglets tanks. Not silly at all. I've been doing it since losing the Mantellas.

[DKOOISTRA]

I wonder too how tank size impacts this, the smaller the tank, the faster the buildup? Also, typically, the smaller the tank the less plants etc...
Derek

[Philsuma]

Without a doubt, the smaller the tank the greater the risk and the faster the build up.

also...

The "Less Vertically oriented" tanks....or the squatter, lower, flatter tanks? They can quickly fill up with CO2 and become death traps.

[DKOOISTRA]

i had a group of 7 aurotania that i lost in 1 night. tank was on the same rack all the others were, all the other frogs were fine. The only difference was that tank i used cellophane to seal off instead of glass. all my tanks have glass over the exo lid with about a .25" gap, that one was sealed tight. I thought maybe, maybe it was a temp issue(?) where it got too cold, we had a real nasty bought here a while back, but i bet it was co2 as all the other tanks were ok. It sucked, bad.
Derek

[dynekevin]

bump^^ for an interesting read

[Philsuma]

TWI saw fit to publish this exact article in Leaf Litter.

It is real. It can happen.

A lot of bad info getting tossed around on DB lately. More than usual.

[Michael Lawrence]

Phil your'e the man, I knew there was an actual thread on this. You may want to link it over there. Too many unknowns in this hobby still for people to blow off an experienced based hobby related fact and toss out other BS statements. I havent heard of a dart starving in a long time. Especially in the viv of an experienced hobbyist.

Michael

[Tony]

This is gonna sound silly, perhaps....but....

I tend to blow into the vivs when I open them to feed, water ect.

This causes the plant leaves to move, shakes up the exisiting, uneaten fruit flies and also helps to dissipate any low lying CO2.

I do the same thing with the few top-opening tanks I have left.

[Philsuma]

Still good to do (air circ) in any kind of viv. Stirs up the excess FF and just moves the stagnant air a bit.

Better than not doin' it huh ?

[RichFrye]

I'm not sure what the exact conditions would need to be to accumulate enough CO2 to kill frogs, but my low light, no or low circulation (in some cases only lighting thermals) and constant breaking down of leaf litter has not caused any known CO2 deaths. I'm sure it can happen , but not knowing the exact conditions in which it will build up to cause deaths makes it a bit mysterious.
If I had to guess, I'd put CO2 deaths at about a frequency of spiky brom impalement.

[Philsuma]

Could be rare, especially for us seasoned /advanced hobbyists....but it's a cautionary tale for newbs.

I am 100% sure I lost a tank of subadult leucs to this very thing. A tight lid combined with high 70's to low 80's heat. Could be CO2 and/or hampered respiration. Ties in with ventilation and air circulation issues.

I thought for sure I saw lots of venting on your Vivs, Rich.

[RichFrye]

...I thought for sure I saw lots of venting on your Vivs, Rich.

No, some have none.
All the acrylic 'cubes' have only one 1.5" vent, circular. The other stuff would all be what I consider low ventilation. Only opening the vivs and thermals as circulation.

[pa.walt]

This is gonna sound silly, perhaps....but....

I tend to blow into the vivs when I open them to feed, water ect.

This causes the plant leaves to move, shakes up the exisiting, uneaten fruit flies and also helps to dissipate any low lying CO2.

when you are blowing into the tank aren't you blowing co2 in the tank. thats what we exhale correct. i told a friend i did this method and this is what he mentioned to me. we exhale co2. just something to think about.

[Philsuma]

It would be CO2 if the breath would be administered via a closed system, like a straw for instance. By having the doors open while expelling breath from a distance, the resultant swirling air currents would contain much 'outside' air and definitely not much CO2.

so...IMO Walt...No.

[dynekevin]

I do not think when we exhale its all co2 though right? If it was, i dont think mouth to mouth resuscitation would work.. right?
Someone feel free to correct me on this one.

But i agree with phil, blowing from any kind of distance will push in a bunch of fresh air and unsettle any co2 / stagnant air.