Hang in there, someone who's had some experience with this is bound to chime in. 1200 LPH filter should be sufficient to filter a 75gal, it looks comparable ... judging by the pics online to a Fluval 406. The best advice I could give is just keep up on the maintenance.
75g Planted Barbs Denison, BlackRuby, Tiger, Albino Tiger, Green Tiger, Cherry, Gold, Checkered, Odessa.
NonBarbs Cardinal, Neon, RummyNose, Bloodfin Tetras, Z. Danios. 1RTS. Amano, Bamboo, Ghost & RCS. 20g Long Shrimp Tank RCS, Tiger, Amano.