All Anableps need brackish water, except for the "false" Anableps, which is actually a mullet called Rhinomugil corsula from India (though it also does well in brackish!). Salinity isn't critical, but 25-50% seawater salinity is about right, say SG 1.005-1.010.
Maintenance of these fish is odd. On the one hand, if you get decent sized, well adjusted specimens they aren't especially difficult to keep. Wildwoods had some specimens something like 15 cm long, chunky as mollies, and they devoured anything thrown to them! These specimens promptly got sold to the London Zoo.
On the other hand, if you get crummy, undersized specimens your work is cut out for you!
In any case, water depth doesn't matter, but breadth is important. Given adults are some 20-30 cm in length, you're expected to use a tank something like 120 cm long and, say, 60 cm broad. The more surface area the better. In the middle on the tank place a flat stone (e.g., a slate) on a couple of flowerpots or similar. Make a table, with the flat stone a few cm under the water surface. The Anableps will rest on this slate.
Cheers, Neale