Slim pickins. There used to be a respectable mom & pop over in Colonial Park named Paxton Aquarium (or similar) but sadly they recently closed for good. Also used to be a place in Mechanicsburg on Trindle Road, but again... think they closed in the past year or two.
Only one remaining I'm aware of is Zootopia Pets on Derry Street, Harrisburg. Some people have poor impressions of them. I recently went in anyway and found it so be not great, but not awful. They specialize more on the reptile/small animal end... but they have small/okay selection of saltwater fish and coral.
Unless I'm unaware of another LFS, TFP remains king of the area.