Snails such as trochus, nerite, astrea( cant right themselves if the fall so you have to do it but are amazing algea eaters) and blue leg hermits crabs.
Dont use the 1 snail per gallon rule they will starve and die and cause mor nutrients, I would say for a 30 gallon
2 astrea snails
4 nerite snails
3 dwarf blue leg hermits
That should take care of most types of algea, if you ever get bubble algea then get a emerald hermit crab but be careful sometimes the eat coral