Bugs in hanging basket

[ItsNotOnlyTheGoodBits]

I'm new to this gardening lark and only have a patio, so only tubs and hanging baskets for me. Even so, I have cultivated quite an impressive dead plant museum!

Anyway we bought some ready planted baskets last year and most of the plants in them have died. So I bought some new pants today to put in them. I dug out the remnants of the old plants from one and replanted with the new stuff.

Then when I started doing the second one I was surprised to discover there was nothing to remove. No dead roots, no stalks...nothing. Upon closer inspection I saw that the soil is teeming with life. Bleurgh! Lots and lots of not so tiny little bugs crawling all over the soil and basket.

Now I am guessing this isn't good. So should I discard this soil and use new? Or is the soil salvageable?