If mushrooms multiply that fast in other peoples tanks I must really be doing something wrong. Either that or they are manjos. Hopefully someone who has had them before will chime in soon and give you a positive or negative on the Manjo thing.
Joes juice or aiptasia X will take care of them pretty quick if they are manjos, but make sure to get ahead of the problem. I have had more luck with the Aiptasia X simply because of the applicator. The Joes juice applicator seems to clog up just when you need it to work the most.