Just the biocube is like $300
And i set up my 30 gallon with fish and sand and plants and filters and everything for under 300. I already had a stand tho.
And dont take my word on the co2 thing. I dont have experience with high light plants i was just told that higher light makes them require more nutrients.
And i dont think the bioballs would be good for freshwater anyways. Youd have to.buy the media basket mod to put pads and carbon etc. In which is $50