You can get away with less but really for optimal health and wellnesss you fish should be fed at elast daily and preferably 2 times a day. Most of the fish we keep in our reefs constantly feed throughout the day in the wild either on algea, plankton, or benthic fauna. Less feedings can help with nutrient management but will also impact the lifespan and health of the fish over the course of years.
I feed twice a day, first thing in the morning and then again after I get home from work.
You can get away without feeding for about a week, I would say, but any longer then that and there may be issues, especially if you keep fish like anthias which will get aggressive to their own kind if food runs scarce. I wouldn't go that long very often though, but if you leaving town for a week or so you should be fine. Any longer then that and you will want someone to feed them at least once a day if not twice.
How often the fish need to be fed really depends on the type of fish. Generally, larger predator fishes are fine going longer times between feedings. But smaller fishes like dartfish and anthias have fast metabolisms and need to be fed more frequently.
Ya you should be good then. I have left for that long several times and I just give them a good meal before I leave and they will be fine. I havent had an issue with it yet
I've done 4 days without a problem. You should be fine. Be careful not to over do it right before you leave. I can see that causing more problems. Instead of one large feeding right before you leave, maybe spread it out and feed smaller portions a couple times that morning so less food goes uneaten.
I have gone 5-6 days without feeding when the fish are otherwise healthy.
I can tell you that I came back once to (good) a foxface that decided to eat all of my bryopsis and (bad) a flame angel that decide that it liked clams mantles and zoas.
I would say it really depends on what kind of fish you have. If you have any "reef safe with caution" fish, you will finds lots of snails and coral missing. I would put an autofeeder on if that is the case. If you only have reef safe fish, you should be fine for 4 days no problem.