GAC can help.
Removal of any filter media like bio balls or ceramics or anything in a high flow area to encourage localized ammonia oxidizing/nitrifying bacteria.
Cleaning detritus out and the sand bed too if there is one.
A denitrator of some type will work.
I've used a diy sulfur dentirator in the past with very good results.
Organic carbon dosing( vodka, vinegar,etc) will also keep them low.
I use two larger asms and have for over 6 years . I like them. You can put a plug in switch in the receptacle and plug the skimmer into that . Then you can just turn it off when you remove the cup. Th skimmer I know of all just keep running when ou take teh cup off and they will all ovrflow. There might be one with some feture I haven't seen.
More live rock or substrate to provide denitrifying bateia with extra surface area may be useful.