Hi:
I will first disagree w/ nellie for making such an unsupported statement and then say that many people like myself (and 1000's of other) who have killer Fo tanks will find FO a better outlet or an additional outlet to a sperate reeftank (i personally will not succumb to full blown reeftank). While the beauty of a reeftank is impressive, so are the colors of emperor angels, lionfish, australian tusk,
colored b'flies, etc, etc,. How many people enjoy the dog-like attention of a large puffer fish?
Many of these fish are unsuitable for a reeftank and deserve their own place. So i say FO tanks are not a dying breed. Just ask me I answer lots of questions of FO tanks
here and
here
Do some people eventually switch over to reeftank? yup
Off my soapbox......
bigger tanks are better, 50gal would be small IMO, I woul consider a 75 or 100 a better choice 180's are great. Bigger tank bigger fish, and better water quality.
What size you thinking?
Filtration-two choices....Wet/dry systems (yup they still work) and DSB/Live rock. DSB/Live rock work great for non digging fish, the water quality is better w/ DSB/LR but its more pricey and again no digging fish. wet/dries work great but tend to cause water quality issues, but nothing that dilgence and attention to details and husbandry won't take care off.
What kind of fish you looking at?
frank