Ummm, easy answer... In my tank :
On a side note place 'Mushrooms along the bottom half of the aquarium on an exposed rock. Make sure that currents will be able to supply it with necessary nutrients and trace elements. Leave several inches between it and other corals. Although symbiotic algae called zooxanthellae hosted within its body supply some of its nutritional requirements through photosynthesis it does require supplemental feeding. Supplementing its diet with the addition of trace elements, marine snow, phytoplankton, brine shrimp, and food for filter feeders will help to insure its continued good health.'
Source: http://www.aquacon.com/mushrooms.html
I personally have not had any issues with them anywhere in my tank, high light, low light, high flow, or low flow.