Can you be more specific?
There are at least twenty species known as 'dragon fish'
I suspect you mean the Dragon Goby (also sold as violet goby, green dragon eel, dragon fish, violet eel, sucker eel and lots of other made-up names to make them sound exciting and exotic.)
Around here, they're about £10 for a nine-inch fish.
They are not the evil predatory monsters that fish stores try to describe them as and are actually filter feeders that need small particulate foods & invertibrates.
There are actually three species of Violet Goby:
- Gobioides grahamae is a lot shorter and more lightly built than the other two, has no stripes and although not predatory, is very aggresive towards other fish of both of the same & other species. It is found in the brackish to full marine waters of the Amazon Delta. A freshwater enviroment will quickly kill it.
Rarely sold in the hobby.
- Gobioides broussonnetii is the longest of the three and is a true brackish fish, and will suffer if kept in freshwater.
Often found in stores and often sold as freshwater as they are collected in freshwater rivers where the spawn.
- Gobioides peruanus can be found in freshwater rivers and water systems far inland, but is equaly at home in mild brackish water. It is more heavily built than the other two species and more territorial. It lacks the bold vertical striping and has a larger head.
We have had two in our freshwater community tank now for some time and have just added a third. They appear to be thriving.
Sometimes found in the hobby, but nearly always sold as Gobioides broussonnetii .
These fish can get to quite a large size, and are clumsy, nocturnal & boistrous. Because of this, they must not be kept with skittish fish, or fish that sleep on the 'ground' at night as they will be constantly disturbed by the goby's foraging.