'Tiny dark bugs' could encompass any of thousands of potential bugs. A description of the bug would help identify it, or, if you poke around the soil gently, a pic would be better.

Chances are it was just fungus gnats - they lay their eggs in the compost, the larvae grow there then hatch into the full grown flies. Unless they are in massive quantities they should do nothing more than annoy you - they should not affect the trees health.

Have you noticed any little flies around the house lately? Squish them if so. Problem is, one female can lay hundreds, if not thousands of eggs before she dies, so kill them quick. Let the soil dry out between waterings to get rid of their breeding environment, and either buy that sticky yellow fly tape stuff or one of those blue UV lights that attracts and kills flying insects (available at garden centres/DIY stores).

This, of course, is all assuming it is fungus gnats that you have.

Fungus gnat larvae are white, or nearly so, and resemble little worms (or maggots). They would readily be observed wriggling around the surface when you water your plant. I'm pretty sure that the females lay dozens to a couple of hundred of eggs over a short lifetime, not thousands. GOOD thing for us!!!! :-(

Bigbloomer, you'll need to describe these 'bugs' in some detail, or maybe even take a picture if you want an identification.

There are several possibilities, from pests that might be feeding on the tender roots or (more likely) critters that simply live in containers and feed on the organic matter that comprises the potting medium.