Hi Ray,
Yes, I keep cowries. Most cowries are generalist omonivores.
Most available within the aquarium trade fall into this category. Some cowries are specialist feeders (such as on sponge).
Those that I keep (presently Cypraea arabica, Cypraea eglantina, Cypraea tigris, Cypraea leviathan are simple to care for but I have the advantage of routinely collecting rock loaded with algae and other benthic organisms for them to graze upon. I replenish with a few "fresh" ones about every week.
Perhaps you are able to do this too? If not, I recommend experimenting with various greens (lettuce, spinich) as well as small bits of meat on occasion (shrimp, crab, etc).
Cowries are generally shy and retiring animals and should be offered places to hide during daylight hours. That said, even though they are primarily nocturnal, they will roam the tank during daylight hours.
Most cowries are from the tropics but not all. For instance, Cypraea spadicea ranges as far north as Monterey Bay, California. Unfortunately, it will show up in the aquarium trade and many will think it is okay to keep in a reef tank, which of course it is not.
Another caution, if cowries are stressed, they may produce a large amount of gooey, clear slime. Fish within the same tank may suffocate and die from this stuff clogging their gills. Although this is rare, you'll quickly understand what I'm talking about when you see this stuff. Just be sure to get it out should it happen, either by siphoning or by using a fine mesh net.
Lifespans vary with species, larger ones tend to live longer.
If you can provide a picture or id the species yourself, I may be able to offer more specific information.
Cheers,
Bob
