You must keep your phosphates, nitrates, nitrites, and ammonia levels at bay. You will do regular tests to determine what levels your tank is at and then add aquarium chemicals and water changes to help keep your system properly maintained.
As for the tree in the sump part. We are referring to an eco system within an eco system called a refugium. A refugium can be located in your sump or incorporated into a hang on the back style refugium system. Most sumps are, or can be partitioned, to have a low flow area before it reaches your return pump, so as to create a refugium compartment.
A refugium compartment holds a sand or mud bed, live rock, chaeto morpha plant, and usually some mangrove plants as well. It is also necessary to have a low level light source over your refugium. I prefer an L.E.D. bulb equivalent to a 40 or 50 watt regular bulb.
As water passes through your refugium it creates a sort of natural protein skimmer to fight against those nasty nitrate, ammonia, nitrite, and phosphate levels. It can also keep you out of danger if you happen to be late on your regular water changes.
So slap that tree under your tank, just another way to help safeguard your investment!
