my friend has a 10 litre tank and it contains 1 dalmation molly, 2 goldfish, 1 shubunkin, tuxedo platty and a red finned black shark they all seem ok and happy is this safe and ok.
2 gal tank, it shouldn't have a lone molly in there never mind the rest, a goldfish needs a least a 20gal for the first fish, then 10gal for every other fish added, as they are big waste producers, good god the shark poor thing need a 40gal tank, and they are aggressive, i would tell your friend to return all the fish to the lfs, as all that tank is good for is a betta.
well tell him he is gonna need a huge tank for the shark, at least 30gallons for the goldfish and at least 20 gallons brackish tank for the molly and other mollies to keep it company.