What kind of goldfish are they? Fancy goldfish (the kind with double fins, odd little bumpy "hoods" or strange eyes, and a rounded body) need 20 gallons for the first fish, 10 gallons more for each additional fish, and tons of filtration. Goldfish make a lot of waste so they need major filtration and tank space. Common goldfish and comets (more slender bodies and a single tail fin) are pond fish and need at least 55 gallons just for one fish, preferably much more because they get to be a foot and a half long ideally. If you have fancies you could keep up to 4 of them in the 55 gallon with no other fish and rehome the tropicals. If they are commons you should return them. The two sharks will likely have problems as they grow up, they tend to be territorial. A 55 would be fine for one though, it would give him enough room to get his own territory established. The plecostamus probably needs a new home as well if he is a common pleco. They can get over two feet long! They also are major waste producers. They need 120 gallon tanks. If he is a smaller variety like a bristle nose, bushy nose, clown or pitbull Pleco the 55 would make a wonderful home for him though. Do you have a heater? The goldfish don't need one, but if you decide to keep the tropicals you need one. You said you are moving the tropicals, but if it were me I would move the Goldie's and the Pleco to the 55 and leave the sharks in the 10 for now, or just move everyone to the larger tank. They have a much smaller bioload than the goldfish so there are two main benefits to this arrangement until you can sort out which fish to keep. The water quality will be better with the high bioload fish in the big tank and it will cycle faster than if it just had the two sharks in it. Also, the goldfish would get sick quickly if multiple goldfish were kept in one 10 gallon tank for long, even with regular water changes.
