who is the culprit fish?

Hi! I'm not an expert, but I would suspect the sharks first. They would be the most aggressive of all the fish you described. The angelfish are cichlids and are mildly aggressive, but I have angelfish and they've never attacked the smaller fish in their tank. Unless your algae eater is over 6 inches long, I wouldn't suspect it, either. I would worry about the sharks. Perhaps there are certain fish they shouldn't share a tank with. :-)

I would guess than Angles depending on how big they are since they are a semi-agressive fish. My mom lost many a neon that way. I doubt your sharks qould touch them unless your little fish wandered to the bottom of the tank. If the golden fish are semi-agressive or agressive, they may have eaten them as well. What ttype of fish are your golden ones? If they are Golden Wonder Kili's then they could have eaten the fish as well.

What are the golden fishes? Are they by chance these fish, kissing gouramis? They get pretty big, and would have no problem eating a smaller fish. http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=968 And, your sharks, is it this guy? An albino rainbow shark, they're white, guess they could look pink in certain lights. http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=1171 Those guys can be aggressive, and unless they're large and the black fish were small, I can't see them eating the smaller fish without leaving something behind. If the angels are large enough, and the black ones small enough, they could've eaten them as well. Depending on what kind of "tank cleaner" you have, they're usually more concerned with eating algae, not fish. They may try to suck the slime coat off of larger fish, but they generally don't eat other fish. As for the small golden ones, if they've already been in the tank for awhile with the others, they're probably fine. I've found that some aggressive fish will be ok with their current tank mates, but when you add something new, they'll eat them or fight with them. I had an oscar living temporarily with some other fish, all kinds large & small, no problems. I had to put a smaller fish in for an emergency, he ate it....Didn't like anything new added in. You should really figure out what kind of fish you have, it's good to know for tank requirements and compatibility issues like you have now. Here's a link to browse through pictures and profiles: http://www.liveaquaria.com/product/categ.cfm?pcatid=830 .

I would say that the sharks, or the angels are doing it. They are more aggressive fish and shouldnt be put in with smaller fish. I would take them out and see how it goes.

since fish went missing shortly after you added 2 new ones..those 2 new black ones would be my prime suspects. you have any idea what kind of fish they are?