Sometimes at the bottom of the tank you can get stagmented areas, which can cause deseases to multiply, best to stir gravel up now and then, it sound like the air buble lifted some debirs into the water causing your test results to alter.
No I wasn't being tounge in cheek, it really is a family forum, so no swearingfatguppy said:sorry Jon - not sure if you were being tongue in cheek with the swearing? If I can't just let me know.
Love the quote by the way from Life of Brian - one of my favourites and gets quoted at inappropriate times in this house whenever possible.