i heard plecos are good, should i get one? and what are suckerfish
NOOOOOOOOOO. Ultimate fail. Most who sell 'plecos' are selling common plecs, which grow HUGE and produce HUGE amounts of waste, totally unsuitable for the average tank. There are some 'plecs' however that are very well suited to tanks eg. BN plec for algea eating, along with lots more, but the fact is most shops who sell pleco's are selling the common or sailfin variety.
Suckerfish, I'm guessing are chinese algea eaters (if the shops sell plecos as plecs, then I'm guessing they mean CAE). They start off small and friendly, but can grow to 10" and be aggressive, attacking other fish and rasping away at their slime coats.
Generally, avoid both fish if you can.