i agree with everybody else.. your RTC probably did eat your arowana. young aros are very jumpy though, so you might want to check the floors around your tank and see if it jumped out. and next time you get an arowana make sure you secure the top of the tank.
plecos do a great job on any kind of algae.. so do snails. but if you want to avoid getting the algae to begin with cut the lights. leave em off for several days and then only turn them on for a few hours per day and the algae won't form to begin with.
