There aren't any eels suitable for a 200 l freshwater tank; at best, you have some spiny eels and of course loaches such as kuhli loaches and fork-tailed loaches, but these aren't eels. Spiny eels are fiddly fish, and you'll want to research their needs carefully before purchase; the vast majority die within a few months. Among other things, the smaller Macrognathus species viable for a 200-l system need a sandy substrate, floating plants, a tight-fitting hood, and generous quantities of live or wet-frozen wormy foods.
In a brackish water system, you could opt for one of the "freshwater" moray eels, preferably one of the smaller Echidna species like the 30 cm Echidna rhodochilus. Morays are reasonably hardy, but it appears that much mortality could be down to inadequate diet, thiaminase in particular being an issue and needing to be managed in the long term by providing an appropriately varied diet of thiaminase-lacking foods (i.e., not shrimps, not mussels, and not feeder fish).
Cheers, Neale