you'll get HH feather dusters and sponges growing in all the dark places of your tank. aptasia are a nightmare, they spread worse than wildfire and can even pretty much come back from the dead.
I once heard of a guy setting up a fuge type thing filled to the brim with aptasia, but to prevent them from spreading to the DT, he had a massive UV sterilizer right off the tank.
IMO there are better ways to control nutrients than aptasia. A lot of soft coral like 'dirty' rich water. Xenia to name one. actually the gonioporas liek dirtier water w/o skimmers but their requirements are still very hard to meet in our tanks.
