aquarium maintenance

Hi! I currently have 3 tanks - a 250g reef tank, a 50g ish fish only tank, and a 40g ish decommissioned jelly tank. The fish only tank is at my home and the other two are at my office. They all have been and currently are being maintained by a company since I've had them (about 4 years)...

So this thread is for the few hobbyist that rely on HOBs solely to achieve their beautiful tanks. My questions are what are you using and what does regular maintenance consist of for you? Aside from the regular water change when are you swapping out your media bags. What chemicals are you...