A plecostomus certainly is the best option in fighting algae, but in some cases it isn’t feasible.
I had a small pleco in my 30 gallon aquarium as well as a featherfin synodonis catfish. The synodonis is a good 6" long and apparently, quite territorial. When the pleco got to be around 4" or so, the synodonis regularly beat the crap out of him. I tried removing the pleco on numerous occasions, letting him heal in a hospital tank, and re-introducing him–and within a few weeks, have to take him back out again.
That pleco now has a nice 10gal to himself (shared with some mellow glass cats). The 30gal, however, is becoming algae-overridden. My solution has been to use those algae tabs they sell in pet stores. Clean the tank, do a water change, and drop in the algae tab–and voila! No new algae growth.
Bleach is not recommended. Fortunately, goldfish are fairly hardy stock.