Hi there, is this a standard 30 gallon which is 36" x 12" x 12"? or a 29 gallon which is 30" L x 12"w x 18"H?
If it's a terrarium of this size 4x 24" fluorescents will do just fine but indeed if you have a Power Compact setup of at least 100 watts that can be evenly distributed over the tank (such as 2x 65 watt fluorex worklight bulbs) I say go for it the plant will love it! I use 6 x 40 watt fluorescent tubes over my 75 gallon lowland tank (where that ampullaria grows). My suggeston is to get as much light over your nepenthes as possible. While plants like N. ampullaria and N. bicalcarata are considered lowlight they do need bright light to pitcher well and grow quickly as possible. Lowlight in a terrarium (say one or two 20 watt flourescents) VS lowlight or semi shade in the wild is much different.
As I already mentioned the lights will also heat things for you up during the day which really helps lowlanders with growth speed. N. amp is rather slow to begin but once it gets to about 30 cm and starts creeping along the ground then shoots pop up all the time!
Yes, if you can build a false bottom of eggcrate and PVC plastic piping that would be ideal! I use the false bottom method for my 75 gallon lowland tank and it works excellent. An ultrasonic humidifier isn't necessary for this kind of setup and will actually make things too wet in such a small space. The natural evaporation from the soil surface in conjunction with keeping the lid closed and covered except while servicing the plant will keep your humidity high enough in the 80%+ range.
If you were to setup as a false bottom I do not think it would be necessary to use a pot since the water would be drained away. Leave the water in the false bottom until it reaches the bottom of the eggcrate then drain it. But leave enough in there so the water will evaporate and will pass through the soil and transpire into the air inside the terrarium. The plant could also much more easily grow in the carpeting fashion you desire if planted directly in the soil of a false bottom tank, I'm almost tempted to give this a go myself! I've got an empty but equipped 29 gallon...
My suggestion for the soil in this setup would be to use a lot of freely draining materials for the substrate such as american spahgnum moss sold by Mosser Lee at most US garden centers. Many people say new zealand sphagnum moss is the best and it is quite great stuff for some applications but the US stuff is very coarse with many twigs, roots, etc. in it which are slow to breakdown and offer excellent drainage.
To this I wouldmix in about 10-15% oak leaf mould (crushed leaves that you can get at garden centers) this will acidify the soil without weighing it down or inviting lots of micro organisms that peat seems to. To these two I would finally mix in some horticultural charcoal to keep the soil fresh for as long as possible. If you can't find the cheaper Mosser lee US sphagnum then the NZ sphagnum mixed with about 50% fine sized orchid bark (1/4" size chips) will give you slowly degrading and fast draining substrate. If you want to add a green carpet of moss overtop the actual planting soil a top dressing of chopped NZ sphagnum will come to life much better than the US sphagnum for some weird reason.
Above all for the soil mix I would avoid using any peat because in such a setup as this. In my straight planted terrarium trials I've only expeienced very horrific smells and eventually compacting soil when using peat or even peat substitutes such as coco fiber. It's just not free draining enough for this kind of setup in my experience and never seems to dry out.
Before you pour your soil mix on the eggcrate put down a sheet of "weed barrier" from the garden center this will allow drainage but keep the soil from falling through the eggcrate and hopefully keep the roots from penetrating into the water below.
Hope that gives you some ideas!
