unconventional reef fish?

[Piscans]

what are some examples of unconventional fish species that can possibly live in a saltwater aquarium?

requirements:

must be able to live in a 40 gallon tank for its whole life

must be compatible with mollies & small freshwater fish if i decide to move it to saltwater for any reason (rainbowfish, dwarf chiclids, corydoryas)

must be cool & not common (not the obvious fish like mollies, common mono, scats, etc.)

 

[davidcalgary29]

There just isn't a huge list of euryhaline fish that are small or colourful enough to be suitable for an aquarium. The orange chromide is a possible candidate, but I'd just consider making your build a brackish tank or paludarium. That will expand your list of possible species greatly, and be much easier on the fish than getting them to acclimate to much higher (or lower) salinity levels.

 

[Steve and his Animals]

Signifer rainbowfish (Pseudomugil signifer) are a brackish species of rainbow that should be able to tolerate freshwater with sufficient hardness for their whole lives. Never tried to adapt them to full saltwater, but I'm sure it's possible with certain localities.

Pseudomugil cyanodorsalis is a tinier species of rainbow that is strictly brackish/saltwater, they're beautiful, but they tend to live only about a year or longer.