Not strictly true StarOrbs. If you have a plenty big enough tank they should come out more than alot of species of Syno. I have read reports of Euruptus swimming around alot during the day.
If you want a tank for Syno. Euruprus, make sure you have nice big boulders or bits of slate, alternatively bogwood for them to hide in. If you have a big tank get a nice small group of them and they will be at their best.
Remember, you will need a ditherfish anyway, something like a large tetra, congos, rainbows etc. or things like Silver Dollars and other larger characins would work fine.
Ben