yes, as long as you have as your tank is large enough for them both.
Plecostomus are algae eaters they are not carnivores. They are also tropical fish so they should never be in an aquarium with coldwater fish like goldfish. If your Plecco is eating your goldfish you must be doing something very very wrong. Work it out. They can live with your goldfish but this may happen, This is because you are not feeding them enough most likely.
Yes. Aslong as the gold fish (coldwater fish) and the pleco (warm water fish) do not go into one extreme or the other on the temperature scale. Your plecostomus will look like it is eating your goldfish if it doesn't get enough food.
Plecostomus are famous for attacking and eating goldfish! NEVER put them in a pond or aquarium together. Many people think that plecos are vegetarian, but they are omnivors. If they are hungery, they will eat what ever they can get in their mouths, and gold fish don't swim that fast! Seperate those fish or in time your goldfish will be gone! As long as you are feeding it okay then it shouldn't eat your other fish.
I am guessing that you mean a Plecostomus. The answer is NO. Each of the species needs totally different conditions. Goldfish are cold water fish and suffer when the temperature goes over 75F. Plecostomus are tropical fish and suffer when the temperature goes below 75F. They will both survive for a while in one anothers parameters but eventually they will die from living in the wrong conditions.
Yeah because they both eat algae and they both are bottom swimmers.
yes
No. Goldfish are freshwater fish and tropical starfish are saltwater fish.
A Plecostomus can live by itself.
Goldfish and cichlids have different care requirements and temperaments, so they may not live peacefully together in the same aquarium. It is generally not recommended to keep them together.
The best thing to do is ask the shopkeeper in the fish shop and find out first but goldfish go together with no problems if you are lucky because some goldfish can't live together. http://en.wikipedia.org/wiki/Goldfish
The number of goldfish that can live together in a single tank depends on the size of the tank and the type of goldfish. In general, it is recommended to have 20 gallons of water per goldfish to ensure they have enough space to swim and thrive. It is best to research the specific needs of the type of goldfish you have and consult with a pet store or veterinarian for guidance on the appropriate number for your tank.
As far as waste producing, this is probably a toss up between a goldfish or a plecostomus. Both produce a high volume of waste, and it's for this reason that hobbyists recommend larger tanks for goldfish.