I had good luck with Neem oil when flea beatles attacked my tomatoes and peppers. I've had to repeat it about every 2 weeks and after it rains. I don't overhead water so it doesn't wash off unless we get some rain - which hasn't been much this summer.

Thanks Jeanne, much appreciated. You are spot on. It is Cerastium glomeratum (Mouse-ear Chickweed). And edible as well.

What is "large"? What is "decent" height? How long are you hoping the tank will last/survive? Depending upon where you live, the plants you gather may or may not need a cool/cold dormancy. Some annuals may produce seeds that require stratification to germinate. Drainage layer is unnecessary unless planning on water feature. Instead make sure all of media is a rather light "airy" mix. Addition of perlite, bark, and/or gravel can help in this matter if using soil. Type of media you plan to use will be a factor. What are you planning on using for a light source? Window lighting will not be sufficient in all likelihood and if the sun is allowed to shine on the tank, high odds of overheating and killing everything in the tank. With what will you be watering? Most tap water is high in ds (dissolved solids) and -- especially if "city water" -- will often contain fluorides and chlorides. Regular filters like a Brita will not remove most of the solids nor all of the fluorides (can't remember if it will remove the chlorides). As such, using tap water is generally inadvisable as it will eventually kill the flora in the tank. Rain water, distilled water, or RO water should be used if you want the tank to live a longer time. Sealed tanks tend to have major fungi or bacterial issues. And unsealed tank (can be mostly closed off just not totally) and/or with one or more pc fans installed inside is recommended.

OK - it was just the turn of phrase. It sounded as if you thought maybe the Trollius had turned into Buttercups. If you're not totally convinced about the id you could wait for the first flower. Or look for the stolons starting to expand their territory.