the small amount of copper could have an adverse effect if accumulated over time as inverts have no way of disposing of the copper in their systems. it's poisonous to them.
also keeping him in a tank with chiclad he was probably stressed out as chiclids are rather aggressive. the crab wouldnt have drowned as they can stay under water and take oxygen from the water.
even though LFS will sell red claws in community tanks they do much better in species only tanks where there specific needs can be met.
red claws come from mangroves in malaysia where the watter can be a little on the brackish side, the salt in the water helps with their molting as it disinfects potential disease and helps suck the moisture out so their shells harden quicker. when a crab molts it is most vulnerable to disease and stress.
in the mangroves the crabs also have easy access to the surface where the majority of the time they spend above water on the roots of the mangroves. though most lfs sell them submerssed they really do better in an environment where they have access to land and water. which also mean you ned to have a tight fitting hood or the crabs will become adventursome and go for a walkabout.
they also do better with lots of hiding places preferrebly wood to match the mangroves twisted framing of roots. after they shed they are vulnerable and will hide if they molt and dont have a place to hide and are with fish the fish may pick on them or stress them out.
as far as lighting goes they do better as most inverts do with true blue actinic lighting as it promotes healthy growth and is a subdued gently light that doesnt stress them out.
as far as feeding goes i fed mine, frozen blood worms, dry sinking crab pellets, frozen shrimp, pond snails and their favorite, peas.
they also do better in sand substrate rather than gravel as i assume your chiclid tank had stones rather than sand. crabs will stir the substrate at night scavenging for food and it's easier to stir sand then gravel.
as far as tank mates go for crabs other crabs can be good but they need space, atleast ten gallons/ crab and two or three hiding places for each, bottom dwelling fish arent a good mix as most dont tolerate any salt and crabs will attack them. they've also been known to sang other fish. puffers do well in salt but puffers will bite and pester and even kill crabs. when i kept mine they were just sanils and a few shrimp in the tank that i'm sure if the crabs got a chance would eat the shrimp.
also a side note is they tend to be very dirty and need to be in a tank with a good filtering system.
in conclusion just becasue the fish store says they make good community tank mates doesnt make it so. the LFS doesnt care about the crabs or your tanks well being they care about making money and they know that most people want a diverse tank. that having a diverse tank though cant meet the needs of all the species in the tank.
in the best interest of the species you buy they need to be placed in a tank where each of their specific needs or as many as possibly can be met so they have a chance to thrive. it's tricky to find species that fit the same needs and the lfs usually doesnt take this into account. your best bet is to read about the species and it's needs you intend to buy and match that with other species you intend to buy.
that way you'll have a happier tank and you'll save money as your pets wont be dieing so often.
I ended up buying a Hagen CO2 system:
/www.bigalsonline.com/catalog/produc...id1=3349;pcid2=
