TNT,
I also agree that mushrooms can be a PITA, but for beginners they are great because there so hardy. I also know advanced reefers that keep them too, but always under control.
After my second year of reefing I set up a mushroom farm tank and propagated hundreds over a period of about 6 months. The easiest way I found them to spread was due to the following:
>nutrient rich water
>low to med light
>gentle constant flow
>additions of Reef Iodide
Well that's why I think that mushrooms don't spread too well in many established reef's, as the water is usually too clean, the light is too bright, there's more than gentle flow patterns, and Iodide is not usually supplemented.
You could always start farming them in a 5-10gl nano with a single pc, a small filter for current and weekly additions of Iodide. Be careful though as some people get confused with Iodide and Iodine. Iodide is converted to Iodine that is toxic in any tank so be sure to use Iodide that's specifically for reef tanks and use it as directed-don't overdose! Also to help speed up the propagating you can take a clean sharp razor blade and make a partial laceration across the top of the shroom, this will help speed up the division process.
Goodluck and be careful, those shrooms can spread like wild fire
