All single-tailed varieties of goldfish will, if properly cared for, live at least 20 years and grow to about 10 - 12 inches in length. If you keep them in too small a container, their growth will be stunted. I'd never use any bowls for 3 reasons:
1) inadequate surface area (particularly in the standard shapes)--at worst, they'll suffocate to death, at best, they'll be stressed and uncomfortable
2) not enough space for swimming or for adequate filtration, plants, etc
3) distortion of light--the curved surface makes the fish confused and unhappy
The algae eater is a pleco? How large? When plecos grow to about a foot or so, cichlids usually ignore them. Some plecos grow to several feet, but hopefully yours isn't one of those species
Watch out, because cichlids will even pick on or eat loaches and other bottom-dwellers. Plecos are good because they are armored well and grow large. And khulis are usually patterned a yellowish lighter color and a blackish darker color.
About how many inches are the cichlids, measured from the nose to the base of their tail? There are many different types of cichlids, but the African lake cichlids that are usually kept together are very aggressive. It's recommended that you either keep them separately or get a large tank and stock it with several different individuals, which will keep them all going at each other, rather than a bully or two constantly picking on a single target. If necessary, you might want to get a tank divider, which will keep the larger cichlid from attacking other fishes.
And remember that to give fishes enough oxygen, the smallest freshwater tropical fish (up to 2 inches) will need 24 square inches of surface area per inch of body length; the smallest coldwater fish will need 48 square inches of surface area per inch of body length; and the larger the fish, the more surface area they need (ie one 10" fish will need much more surface area than five 2" fish or ten 1" fish).