Well, it's probably a 10 gallon, since that is the standard 'small fishtank'. Just to make sure, can you measure it and give the dimentions in inches? Or figure it out yourself, by doing length x width x height (all in inches), and then divide by 231. The answer you get is the number of gallons. Good choice on removing the cactus, as they are totally the wrong choice for a terrarium, especially one that is using potting soil and is probably in low light. Potting soil is fine, but it would be better if you could add some extra perlite to it to increase soil aeration. And it only needs to be 2-3" deep. I would vary the height to make it more interesting. For example, you could make the back higher than the front, or make it slope to one side. For plant suggestions, since this is a classroom terrarium that will probably not get a lot of maintenance, I'd stick to plants that stay naturally small, and will not need constant trimming to stay in check. A mini African Violet would be a good choice if it doesn't stay too moist. The glass cover should allow a little crack to let air in and excessive heat out. A mini fern like 'Fluffy Ruffles' would also be good (all other ferns will get WAY to big in a year or less). Selaginella kraussiana or uncinata (club moss) would make a good groundcover. I like the 'aurea' (golden) version of S. kraussiana better than the regular green, because it really helps brighten things up in the terrarium. Some ferns may naturally start to grow in the terrarium just from spores in the potting soil, and they can be left, as they will take a very long time to gain any real size, and depending on the species, may never grow large. You could also add a neat piece of driftwood or some nice rocks to the landscaping. An air plant (tillandsia) could be attached to the driftwood. Just make sure you pick one that enjoys more moisture (they appear more green, others appear more silver) and stays small. T. stricta or T. ionatha might be a good choice. Hmmmmmm. . . . fittonia is great for low light, but is a rampant grower, as is Ficus pumila. . . same deal with english ivy and wandering jew. . . You could plant the smallest Neanthe Bella palm that you can find. It will be good for a few years before it outgrows the tank. A small cryptanthus might be good, but they will revert to plain green if not given enough light, and will form a large, spreading clump if happy, so maybe not the best choice. DON'T plant an aluminium plant or polka-dot plant. They seem to be perfect terrarium plants because of their small leaves and slower growth habit, but they rot and drop their leaves easily in that much humidity. If you don't mind spending some more money, and you like Rob's Violets anyways, you could place an order with them. They carry many mini plants. Check the link below. Here is a link that might be useful: Rob's

There are actually quite a few candidates depending on the conditions you wish to provide. There are a multitude of very small to true miniatures in the orchid family. You just have a bit of research ahead of you. *For cool to intermediate temperatures: Masdevalias, Draculas, Dendrobiums, and Restrepia are some examples. *For warm temps: some mini-Cattleyas, Dendrobiums, and Epidendrums/Encyclia would be some examples.

Pothos (neon, satin, queens ivy,) -- all fast growers; Monstera obliqua, Philodendron Scandens Micans, miniature Anthurium, (also Caladium humboldtii if you don't mind pulling it for a short rest

First and foremost, that is not a fern. Your confusion is perfectly understandable as the common names for such a plant often -- but erroneously -- include the word "fern." In reality, it isn't even a close relative. That plant is actually a species of Asparagus. (Yep, a relative of the type people eat.) It doesn't appear to be dead yet but, as you already know, isn't faring well. This type of plant prefers LIGHTLY moist, well drained soil. (The latter not being truly possible in that container. The so-called "drainage layer" often recommended by folks is not terribly effective.) They also like bright indirect light and, unfortunately, are often prone to pests such as mealy bugs, and spidermites (not to be confused with spiders). Next, 2m away from a north facing window would be the equivalent to light levels not far removed from sticking it in a closet. Something to keep in mind is the amount of light our eyes require for sight is FAR less than what the majority of plants require for photosynthesis. Our eyes are really very sensitive in comparison. Molds are pretty much inevitable in a container like that. The lack of air circulation coupled with a lot of moisture creates prime conditions for fungi/molds. Your watering situation is likely a big factor. As you have discovered, overwatering is frightfully easy to do and once done can't easily be undone with containers like that one. It is possible that during the time it took the media to dry out from the overwatering incident, that the "fern" lost most or all of its roots. It sounds like you have switched up the watering several times. One possible problem with that is the stress such changes place on the plant(s). For example, if the "fern" lost its roots during the "flood", it may have started to send out new roots once the media dried out to "moist" levels. But if you perchance erred by then allowing the media to get TOO dry, those new roots may have shriveled up and died. Lest you feel like an awful "plant parent", keep in mind that little jar or vase like terrs such as yours -- although cute -- are actually not easy to keep healthy for any length of time. A lot of trial and error (and errors are often fatal) is generally required for longer term success. Many people and stores keep such as temporary arrangements expected to last no longer than a couple months.