the skeleton....has the flesh removed or receded.....if the flesh receded and what should be bright white skeleton is covered in algae, that is not normal.
or do you mean the old dead skeleton from which it grew.....if the skeleton below the polyp or stalk or base is covered in algae, that is normal. often, because the polyps extend so much on euphyllia species, we dont see much of the stalk or base, but it is normal for the old skeleton below the polyp base to have algae growing on it (hopefully coraline)
for a coral to smell like "fish" is a pretty normal thing. Coral have a fairly pungent odor, but should not smell FOUL.
The white skeleton in the lower part of the coral is fresh skeleton, and it should not be exposed. But it appears as though there is enough flesh that it should recover\heal. that skeletal part that is showing will not recover.
The best thing to do is to put it in low low light and low flow for at least 1 to 2 weeks. in this time, algal growth will be as limited as possible given your systems nutrient load etc. the remaining flesh will not fully extend most likely until it is healed.
keep an eye on it for brown jelly infection, and if it shows, pull the coral and cut the infected area(s) away and remove from tank as it can spread. you can search brown jelly on reef central if you are unfamiliar with it (i hope you dont have to deal with it)
But in general, given proper parameters, Euphyllia are very hardy corals and this one should recover. in a year, you'll never know this is how it started.
If it came from the LFS like this, i would talk to the owner\manager and request money back or exchange. and then be wary and fully inspect corals from them with later purchases.
If you do not quarantine corals, i would restrain from adding anything new until this coral heals so you can be sure no new variables are added which could jeopardise it's health further.
good luck. keep updating.
regarding the smell.
fish is ok.
decomposition is not.
next time you go to the LFS, ask to smell a healthy coral. its somewhat unmistakable. just like your skimmmate in your skimmer should you run one. that is the smell you want to avoid.....ever pulled a dead snail out of rockwork before...that smell is what i am talking about.
do a bit more research on brown jelly. i dont believe it was based on the pic....but its hard to tell
bummer
That looks more like symbiotic algae, but again, may be brown jelly. you did what you thought was best, and probably to your benefit.
i would talk to the LFS, cause that is crap. 2 days....i hope you got it cheap.
if they sold for 12, they knew there was something going on there.....40 is still HIGH for that frag IMO, but when they reduce prices that drastically, be ware. its like discount sushi!
Good luck