I would guess only a handful of people have dendro's living longer then 2 years. Chuck's tank has gonna through some ups and downs. Right now it's on the downs and is moving the living corals into a smaller tank.
Some have even speculated that Dendronephthya sp. don't have lifespans much longer than 2 years. If that is the case, the husbandry practices won't matter. You'd have to find a way to keep it sexually propagating for it to be worth the trouble IMO. I hope that it isn't the case.
I think you can just sum up Dendro's and scerlo's as a whole group as not easy to care for at all. One little power outage hiccup, a few days without the same feedings look at the tank wrong and you can lose it all. Thats what happened with mine. COuldn't get enough food...plus if I could I couldn't afford it either.
He still has some dendro's living, smaller and less polyps then before.
I believe he is moving them to a smaller 30 cube to see if he can recreate his success with them.
I would have to say at this point in time we don't have a means of keeping these creatures in a long term cost effective manor.
I fed my tank Shell fish diet and Roti feast. I'm guessing I would need to spend over 100 a month in food to keep them alive. I noticed though if I missed a feeding day or 2 when I was out of product the corals would take a week or so to get back to opening right and looking good. There just to sensitive IMO.
Chuck's tank took a hit from a power outage. He feeds a considerable amount more then i did, I would guess if you broke the food cost down it would be something like 3-400 a month in food for his tank.
I'd say that, if you're going to have a dendronephthya tank, I would use a small tank (like a 20 gallon) and just buy one and test out the feeding methods. This way you wouldn't have to spend quite as much in feeding, you can handle nutrient levels with high percentage daily water changes (automated if you want), and you can adjust things like flow much more easily. For flow, I would use a closed loop with the intake on one side of the tank and the output on the other.