The leniencies of ketamim (stains) apply only to stains found externally. Once an object is inserted internally, any blood found on it is not considered a ketem, but is comparable to blood found on a bedikah. This is why any blood found on a tampon will make you niddah; you are correct in not using one until you have a "flow." Similarly, any quantity of blood found on a mooncup will make you niddah, independently of whether it is considered mekabel tum'ah. You should not insert any object internally to contain the bleeding unless you consider yourself niddah already.

There are other methods of trying to shorten the bleeding besides the mooncup. We have received reports of taking large doses of vitamin C (some specifically recommend lemon juice, although pill form likely works as well) once the bleeding begins, as well as alfalfa (leaves/sprouts/seeds). There are herbal remedies that claim to reduce the bleeding (such as shepherd's purse) but we only recommend their use after consulting with a healthcare professional (conventional or alternative).

Please feel free to get back to us with any further questions.

B'Hatzlacha!