any ideas on how to find something that's using vis or causing this? we used to have energy to spare, now it seems to not charge up at all.
Well, does the node start to fill slowly, then suddenly lose the vis again? That'd mean it's being used. It may be that other vis nodes are being drained and they're being replenished by this node, in which case you'll see little sparkles heading off in the direction of those nodes whenever it happens.
If the vis level isn't going up OR down, then odds are you've simply run out of vis. Go find a node that isn't depleted and make crystal clusters. Lots of crystal clusters. Actually, go do that anyway, you're going to need them no matter what the case is.
Then why does the arrow point down for the aura while the flux goes up?...
Sorry, but I like to learn as much as possible about, well, everything.
When you use vis for most things, flux goes up. The higher flux is, the more likely "weird events" will happen in your area (eg, lightning strikes during the day, random mob spawns, and, of course, wisps will appear). The events will usually relate to the type of essence that produced the flux, but whenever one is triggered flux levels drop somewhat.
When a silverwood grows, it produces a new pure aura node near the base of its trunk. This LOWERS the vis limit of another nearby node in exchange, and it does so by a greater amount then the maximum aura of the new node produced. You permanently lose vis storage, but in exchange you get a node that can remove flux on its own (without "weird events") and is closer to where you actually want your main node to be.
Naturally generated silverwoods tend to have bigger nodes in them, so if you
want a pure node it's often a good idea to find one of those before settling down. Keeping in mind thaumcraft is quite likely to bug out and delete nodes (some or all) at some random point in time - if you intend to do a LOT of thaumcraft related stuff (eg, fashion your base with things that often use vis, like the elevators), be prepared to pack up and move every now and then, or to cheat new nodes in (by eg using server commands, or tweaking the thaumcraft config files to regenerate them all).
Nodes do not ever charge without help. To actually charge up to its maximum capacity, a node will steal vis from nearby larger nodes (meaning the biggest node in the area can't do this). If that's impossible, the node will convert nearby infused ore to dull infused ore, which gives it a (very small) amount of vis back. Crystal clusters recharge nearby vis nodes for free, but slowly.
