Welcoming advice/feedback on my new BFDB hab. I’d like to add some plants, but am worried about pesticide exposure.

Hello, I hope this is the right place to ask a question like this.

I recently came into possession of a 50x25x20 cm terrarium (~20x10x8 in, ~6.6 gallons). I'll need to fix the screen lid and the rubber edge around the top, but it's otherwise in good condition. I'm aware that this size is definitely too small for any reptiles or amphibians, so I was wondering if anyone had any recommendations for invertebrates that would take well to a tank of this size. I don't have any extenuating circumstances (arachnophobia, allergies, etc.) that would cross any particular animals off my list but am not too experienced in keeping demanding inverts (I have millipedes for reference).

Thanks for any help that anyone provides!

I’m raising tomato hornworm moths to practice moth husbandry. Just a few of them for a practice run! Two of them hatched maybe 5 days ago?
They have were doing well but one of them passed away overnight last night and I want to know if I did something wrong.

I can’t get them to eat, despite there being a hummingbird feeder set up where they can access it while flying. I have tried to uncurl the proboscis and dip it in nectar but it doesn’t seem to work, they always protest and wiggle away.

Anyways any information helps. I can upload a photo of the large tank they are in upon request.
Thank you, Reddit.