Snails and Slugs
So, you've got slug or snails in your vivarium (note that for the most part snails and slugs are harmless your frogs). They may occasionally eat your egg clutches, but they are most adept at eating plants. Generally the more expensive the plant is, the more readily they eat it! Some people think that the more species in the vivarium, the healthier the picosystem. I would tend to agree with them, but I also like having decent looking plants. Therefore, I suggest taking steps to prevent infestation, and attempting to remove them if they are spotted. Ultimately, like everything else, the decision is up to you. Check out my poem about my snail and slug invasion.
Signs that you have an infestation.
Just because you haven't seen any snails or slugs doesn't mean that you are free of them. They can take a while to become apparent. A good rule of thumb is that there are about ten times more slug and snails than you have seen. In my experience the first things that they go for are the orchid roots. One day they will be growing at their usual slow yet exciting pace and the next day it will look like someone broke off all of the root tips. You might also find that the morning dew on the glass has slime trails on it. Next are delicate leaved plants. You will notice that its almost looks like someone took a hole-punch to the leaves. Finally they will go after the developing leaves and start eating your eggs, but by this time they will be apparent, especially first thing in the morning. You might notice that there is a nice clutch of eggs when you go to bed, but the next morning the yolks have disappeared and only the jelly remains. You will also start to notice that leaves either get eaten while still buds, or they appear deformed from being chewed on while developing.
Identification
How did they get here?/ Prevention
Most snails are introduced into the vivarium either in the soil, with the leaf litter, in wild collected moss and among plants. Like so many things, prevention is the key. Here are some tips to ensure that you do not get an outbreak of snails and slugs.
Sterilizing Soil
To sterilize, or not to sterilize? Soil, even if it comes in a nice looking bag, can harbor slugs and snails. It is also full of beneficial bacteria, fungus and other microorganisms essential for a healthy picosystem. So one option is to bake the soil at 250 F for 30 minutes, which will kill the snails and slugs, but also much of the microorganisms. The vivarium won't ever be completely devoid of microorganisms, and they will enter back into the soil from the air, water and terrarium decor, but there will be a drop in diversity. It will also take a long time for the soil system to stabilize. Alternatively, you can just risk it. It's your call.
Sterilizing Leaf Litter
A thick layer of leaves is essential to a thriving picosystem. You can boil or bake them. Bake them at 250 F for 20 minutes or put into a pot of water, bring it to boil and then remove from heat. Boiling your leaves will make them break down faster.
Sterilizing Moss
Take it from me, DO NOT PUT MOSS DIRECTLY FROM YOUR GARDEN INTO YOUR VIV! When I was setting up my first vivarium I sterilized all of my plants and leaves before adding them to the vivarium. Once it was all set up I got overexcited about all the moss growing around Seattle and tossed a bunch of moss into my viv. After two months, all my orchid roots started disappearing. Years later I still had a snail and slug problem. Moss is a bit more sensitive than most plants, but a bleach dip you should be fine. If you are patient (remember, patience is a virtue), I suggest that you break off the tips of the moss and seed it around your viv. After it starts to grow, break off the new growth and move it to another spot. Using this technique will eventually give you great coverage, and moss looks great after it has gradually crept along the surface, as opposed to being put in in large chunks.
Sterilizing Plants
Spending the extra time to ensure that your plants are snail free BEFORE placing them into your vivarium will save you much time and heartache later on. There are different strategies to ensuring snail free plants, depending on the plant. The are generally transported in the soil. If it is a vining plant, a bromeliad or grows well from cuttings, just make a cutting from a stem away from the ground, wash it well with soap and water and put it into your viv. Otherwise your alternatives are to either A) grow the plant in quarantine for a while before putting it in your viv or B) sterilizing it in 5-10% bleach for 5 to 20 minutes. I've never used the bleach treatment, but others claim that it works. Add 1.5 cups of household bleach to 1 gallon of water, soak the plants. After 15 minutes, remove the plants and rinse with water, then soak the plants in water with aquarium dechlorinator, which will inactivate the bleach. Let the plants soak for 1 hour, them rinse again with water and let sit for a day before adding to the terrarium.
How to remove an established population
Combating an infestation of slugs and snails is not fun, but neither is watching you plants get eaten. There are several ways to tackle the problem...
Hand Picking
This is the most primitive, and in my opinion best option. Go to the grocery store and purchase a head of lettuce (doesn't matter which kind). Wash the lettuce, and add pieces to your viv, 1-2 lettuce leaves per 10 gallons. Every night check the lettuce before you go to bed and first thing in the morning when you wake up. Replace the lettuce as it gets chewed up or once a week, which ever comes first. You should make a significant dent in the population after about 2 weeks, and after a month they should be mostly gone. I was able to remove more than 200 snails over the course of a month this way from a 55 gallon tank.
Beer
So, you thought this would be a nice excuse to grab a 6 pack? WRONG! You want to use non-alcoholic beer. Using beer as bait for slugs has been around as long as people needed an excuse for why they left a bunch of beer bottles out in the yard all night. "Uhhhh, it's for the slugs, honey!" Well they were right, beer is an effective snail and slug trap. They go in for a quick drink and next thing they know, they are covered in booze. Sound familiar...
An article published by Colorado State University showed that non-alcoholic beer works just as well as the good stuff. Since it is potentially dangerous for your frogs to be in contact with beer containing alcohol, you will just have to drink that six-pack yourself. I tried setting traps with beer in my vivarium, but was only able to capture a fraction of what I captured by hand picking. If you have had a better experience using beer traps in your viv, please send me an email and I will post your results here.
Sluggo
Sluggo is a slug and snail baited poison. More specifically, it is grain and yeast infused with iron phosphate. DO NOT USE A POISON WITH METALDEHYDE IN IT. Metaldehyde is very toxic to all animals, including frogs. For some reason (exactly how is not known), iron phosphate is toxic to slugs and snails. After they ingest the Sluggo, they quit feeding and may eventually die. When I tried Sluggo, I used way more than the recommended dosage (about 1 pellet per square inch) and saw significant results. My orchids started growing again and the slug damage was definitely decreased. I reapplied the sluggo once a week for about 2 months. After two months I noticed 2 things... 1) The slugs started coming back. These were full grown adult slugs, so I think they must have hidden out in the leaves, and 2) My microfauna was eating the Sluggo. I'm not sure if there was causality, but I also saw a decline in microfauna. So then I quit using Sluggo because I figured that the mechanism of killing isn't known, and the microfauna, which the frogs are eating, is full of Sluggo. But perhaps I was being overly cautious. So in conclusion, I would say that Sluggo will reduce the damage the slugs and snails do to your plants, but will not kill them outright.
CO2
This is the atomic bomb of slug and snail killing methods. Except it doesn't always kill them all. This method works by adding "dry ice" (frozen CO2) to the terrarium and killing the slugs and snails with a combination of high CO2 levels and low O2 levels. Not only does the CO2 kill most of the snails and slugs, but it kills off most of the life in your terrarium. All of your diverse microfauna… dead! Some of your plants… dead! However, some people have had reasonable success using this method to kill off snails, slugs, millipedes, nemerteans or other small invertebrate.
Here is how to do this method:
First, REMOVE YOU FROGS FROM THE VIVARIUM. They will absolutely die during the treatment, if not first removed. Next, purchase some dry ice. You should be able to find a local supplier, and it’s not too expensive. Now that you have the dry ice, seal off your terrarium, everywhere but where you will be adding the dry ice. Now, get a big bowl of warm water, put it in your viv and toss the dry ice into the bowl. It will start bubbling as the CO2 evaporates, and the cold gas will look like fog filling up your viv. Now seal the whole thing up, airtight. Replace the dry ice after about 6 hours and repeat, making sure not to let too much air in. Let the terrarium sit for 24 hours, then remove the dry ice and check for slugs.
About this methods: This is not a sure way to kill snails. I performed a controlled experiment where I exposed slugs and snails, in a Petri dish, to 100% CO2 for 24 hours. The next day 2/10 of the snails was able to recover back to norm (after looking dead for a long time). There are numerous reports of people dry ice bombing the tanks, only to have the snails return. CO2 is fairly effective at killing some invertebrates though, so expect to have to reseed your microfauna. Some people have reported that the mushrooms in the tank will all grow shortly after the CO2 method, presumably because all of the microfauna have quit eating the mushroom mycelium.
