I started my latests batch of IPA (from a Wilko kit) off 19 days ago. Unlike my previous attempts, fermentation began rapidly and consistent. It has slowed down over the past couple of days so today I took the SG. The instructions says that "Fermentation will be complete when bubbles cease to rise (if you use a hydrometer, when the Specific Gravity (SG) remains constant below 1008)".
On both this and my previous batches, the SG has hardly changed at all. My hydrometer has volume scale and it has barely moved off 0%! Any suggestions as to what I have done wrong or should do at the bottling stage?