I have a Fluval 405 in my 75g bow front tank. I have kept a fish only tank for a few years and the filter has worked fine. I plan to empty the tank out and re-make it into a planted tank. I've noticed that alot of people mention having 2 filters. Is this a must? The 405 has worked fine on its own. Besides, I would think that the plants themselves would act as a sort of filter. Sneaking a new light fixture and pressurized CO2 system past my wife is going to be hard enouph! Do I need to add another filter to that list?