Goldfish have no eyelids, and will be shocked and stressed if lights are suddenly turned on. It is a good idea to always turn on room lights first. Fish do sleep every night and will get the best sleep when the light s are off . You should try to get them on a schedule and turn the lights off at approx. If you leave the lights on around the clock the fish will find some time to rest during the day but will remain healthier if they are allowed to get some sleep at night.
Fluorescent fixtures produce more light per watt and give off less heat than incandescent bulbs.
Filters come in various brands and types that will efficiently clean your tank. I would suggest that if your tank is larger than a 10 gallon investing in a undergravel system with powerheads, which creates a biological system within the gravel. I would also use an outside filter system. These use fibrous material and activated carbon which purifies and cleans the water. Tank Decorating Decorating the tank is purely an individuals own preference.