Not brackish. The bit of reading I did on them.. The males are more agressive, and if you have a M/F pair they will mate non stop and pick on anything that comes near. And your CAE... aren't good algae eaters, get agressive, and have been known to latch onto other fish and suck on their slime coats.. Unless you really like em my opinion is to have different fish. That snake thing.... How big? Colors? Any ideas on what it is? (pic?) Any pics of the whole tank??