I use 2 Finnex planted+ (36inch) on top of a 125gal (6 foot). Granted this is shallower than the 180gal.
I use 1 Finnex planted+ (48inch) on top of a 75gal (4 foot), also shallower.
I have been very happy with both. Photos below. This are not heavily planted tanks, and I don't consder the plant performance diverse or outstanding, just plain satisfactory. And it revolves around low-to-medium light plants. I do give root tabs (once a ear?), and Flourish twice a month, nothing else.
I will suggest to start with a relatively small number of plant species (no more than 5), and as things progress, you can add more in chosen places than may appear more suitable than others. Every time I start with many different plants, I end up concluding that I wasted money and time.