I don't think this newly discovered organism is living off the plant so much as sharing its space, enjoying the nutrients and moisture and protection. As such it's probably not a threat to the plant so much as maybe a nuisance (if it clogs up the drainage holes) or just something that's better forgotten. I agree with Daisy. It's probably not an existential threat. I mean sure, isolate the plant and watch to make sure that there's nothing else going on, but I don't think this is the best time to declare chemical war or somehow mechanically cleanse the roots of this thing. Maybe let the inner pot drain for longer when you do water, so that water doesn't pool in the outer pot and keep a body of moisture underneath it. That's what I would do anyway. I try to distinguish between pests and cohabitators, even if I don't know everyone's names.
You mentioned the water seems to just pass through. One perverse consequence of soil going totally (bone) dry is that it actually resists rewetting when initially exposed to water. This is particularly true with peat and also somewhat true with cocofiber and other organic components. Its receptivity to rewetting improves dramatically when it is a bit moist. The first blast of water may mostly pass through, but if you were to wait 5-10 minutes and water again, you'd find that more was absorbed. As a general rule, I like to water in more than one pass, because the first pass only gets the soil moist, without allowing anything close to total saturation (my usual goal).
The thread "Sunday afternoon experiment: watering in multiple passes" in
Gardening Ideas forum
