heheh nice to see you again mudfrog!
ANd it would be best to get rid of everything (move) out of the 55 and add sand and raise sg
levels up very slowly until about 1.008. The tumor thing is true, my cousin has one and a month after getting it it developed a giant orange tumor inside it's mouth that hasn't gone away since. They may live in freshwater sometimes but they don't even close to thrive. THe ones i've seen in freshwater don't do good at all, most have torn fins that don't heal, tumors, messed up scales, and just sit here, while mine is in pretty good condition expect a few deformed fins after an "unfortunate" accident. It's in slight brackish water (1.003) because it has to be housed with other fish att he moment that aren't brackish, it eats during the day and even goes to the top to eat flake, bloodworms (frozen and freeze-dried), and a heck of a lot more.
ALong with the tumor thing there are two other symptoms that occasionally occur with fw
kept DG's, one is liver failure, the second is a bad white skin slime..they usually die a few days after showing these symptoms.
If it's in the 55 you could even go with 2, or even three, but two would be best if you want more. They can also be kept with bumblebee gobies and brackish flounders. Dragon gobies do have the potential to get HUGE but most stop at about 14 inches or around that, the ones you see at 3 feet are usually in huge tanks they're whole lives and are fed a lot.
ANd yes dragon gobies and violet gobies are one in the same fish. You can tell it's a goby by it little "suction" cup fin on the bottom. All gobies posess this, more like two fins fused into one and they like to hook onto the glass or driftwood with it.
Good luck with it, and btw mudfrog..nice gobies again!