If the office keeps to a reasonable temperature range (and most do), a planted vase is pretty much as low tech as you can get. No filter, no heater, just needs a once a week 10-20% water change and a regular desk lamp with a high lumen bulb. Supplies are limited to food for the stock, water conditioner, a jug and a bit of air line hose to do the water changes.
With the close-up nature of a desk tank, the inhabitants can be quite small and simple and still have a big impact. Snails of every sort, shrimp and endlers are all good choices. Neocaridina propinqua are my favorite for planted vases--the orange color stands out against the plants so they're easy to see, they tolerate a huge range of water conditions and-best of all-won't breed you out of house and home like cherries do.