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Bugs getting into a terrarium are a PAIN and they can do a lot of destruction quickly because they’re in a confined space.
There are, however, many ways to deal with them. Different methods with appeal to different people so pick your favourite.
Please don’t buy a predatory animal without doing your research. Granted, we did get our frog on an impulse BUT it was because the guy was going to cull him if we didn’t take him (he was meant to be two-tone and he’s green all over. I don’t know how big of a deal that is, but we’re not breeding him and he’s healthy, so who cares?).
Preventing bugs from getting into terrariums
I mean, this is great if you can wangle it. Ideally, we should be isolating plants before they go into a terrarium. A lot of plants have things like thrips and aphids on them from the garden centre, and you should isolate them for a couple of weeks just to make sure they’re not harbouring fugitives.
This doesn’t just apply to plants (which we learned the hard way). Any moss or substrate can be harbouring fucking SLUG eggs.*
*When it comes to removing slugs, I like to put in something like a piece of cucumber and then pick them out when they come out to investigate. I appreciate that not everyone likes touching slugs** though, so you can fashion some sort of trap if you prefer.
**I don’t LIKE it. That would be strange. But if a slug needs to be picked up, I can do so without screaming/crying/throwing up.
My little froggie eats gnats and aphids. His name is Anthony Hopkins. He also has supplementary flies, so he does too good of a job. We also have four geckos in there that also eat flies.
Yes, it’s a big terrarium (repurposed aquarium).
This method isn’t foolproof. The frog is efficient BUT often you’ll find that the predators would prefer you to feed them rather than catch their own food. I mean, it makes sense. It’s a bit of a waste of energy to troll about the terrarium catching flies when we’re gonna put food in anyway.
Not feeding them until they’ve eaten the pests is, er, cruel. Pets should be thriving, not just surviving!
By the way, no amount of frogs will eat slugs. Unless you’re gonna put an entire duck in your terrarium, you’ll have to get those out yourself.
I LOVE using predatory bugs to eat house plant pests. It’s the way nature intended!
When plants are feeling a bit infested (as you do) they produce extrafloral nectaries to attract predatory bugs to eat the pests. Genius!
See those little dots? extrafloral nectaries! Aaaand on the back –
See those little dew drops? It’s sap, so the predatory bugs can grab some energy before battle.
We have a clean up crew of ‘good’ bugs – isopods and springtails. They eat decaying matter and take up the space that a fungus gnat would like to live, but they don’t cause any damage to your plants roots and, most importantly, won’t fly into your mouth when you’re trying to drink your wine.
You can buy predatory insects like lacewing flies and ladybirds on eBay. They’ll eat every bug and then, er, starve, so leave the lid open after a day or two so they can fly away.
Building up colonies of predatory bugs is probably the easiest, most natural, and safest method of pest control (as long as you don’t mind living alongside them). It’s how most botanical gardens and professional greenhouses manage pests.
Insecticidal soap/ neem oil
I wouldn’t use this in my terrarium, because I would worry that it’d hurt the animals, but if you used something gentle, like castille soap it might help. Just be careful that you don’t use too much, because you don’t want to end up with a lot of soap in the soil.
If this is the approach you want to take, I’d uproot the plants and spray them outside of the terrarium. Yes, it’s a ballache, but it’s better than losing all your plants a month or so down the line.
Neem oil would be a better option, but if you have terrarium lights you may need to turn them down so the neem doesn’t cause leaf burn.
If you’re an organised type of person, you can add systemic granules when you’re building your terrarium, as a preventative measure. I know Harli G adds mosquito bits to her soil mix, which is a great idea.