I couldn't disagree more with the "limited in terms of behavior and lifestyle" comment. The most boring saltwater fish I have ever owned had more personality than any freshwater fish I've ever seen or owned. Just a few examples of some saltwater behaviors and fish that have a ton of personality.
Eels/fish living with and having their mouth and body cleaned by shrimp
Gobies pairing with shrimp and sharing burrows/protecting each other
clownfish hosting anemones/powerheads etc.
Tangs that will follow you around and stare at you through the glass all day long
Triggerfish, which have more personality than any fish I've ever seen
Groupers/lionfish/anglers/rays/sharks/octopus the options and different behaviors are endless.
I can stick my hand in my 28 gallon reef and handfeed any fish in there, get attacked by the clowns defending their anemone, have my hand cleaned by shrimp, and have every hermit crab in the tank race towards my hand to get on it and start picking at my skin. The personality and behavior is just on a completely different level than freshwater.
Also, if you buy healthy saltwater fish, properly acclimate them, and quarantine them, you shouldn't be losing more saltwater fish than freshwater. I'm 3 years in and have yet to lose a single saltwater fish or shrimp.
You severely misinterpreted my statement. I'm not saying that there aren't different and diverse lifestyles of saltwater fish, but there is a MUCH more limited selection. Also, freshwater fishes have increased speciation because land-locked bodies of water have increased genetic drift and reduced gene flow. This lends itself to varied strategies both in morphology and behavior. Tangs behave like tangs, but not all characins (the family including the tetras) behave similarly. The same holds true for many groups available in the hobby. You may have different species of damselfish with different levels of aggression and a few different lifestyles (such as clownfish), but it's not the same as the type of diversity you would see among catfishes. At least not what's available in the hobby. FW fish are more accessible because they can be farmed in man-made ponds.
And you must not have read the entire comment because I made it separate from symbiotic invertebrates. With the exception of the tangs "that follow you around the glass" and the triggers (which usually don't play well with ANYTHING, especially not inverts) that eliminates all of your examples. Triggers, however are known to be one of the most intelligent groups of fish in the world. They possess an enormous telencephalon (fish analog of cerebrum) compared to other species.
And when you buy fish from a wholesaler, you TRULY see what kind of losses you are looking at. Most SW fish are wild-caught using cyanide, not to mention being crammed into closed systems with pathogens from around the world.
You must have small clowns. I do tank maintenance and it's not always so fun to deal with an aggressive tomato clown (sometime large maroons also). They have drawn blood from me so many times I have to use a glove for certain individuals. All crabs and shrimp will bum-rush your hand, but I have yet to see a SW fish jump out of the water to catch food in my hand (I had an oscar and a warmouth that did this). I have also never seen a SW fish stick its head out of the tank and look at me like a spiny eel.
