Wait, so if aquasoil should do fine and all I'd need to do is dose the water column, could i do that with the dry fertilizer? is that what you're saying? lol or should I get something liquid? And I was looking on marinedepot.com's selection of seachem's fertilizers and stuff and they weren't expensive... they were like $4-12 for bottles of things, not like $20 for brighty k on ada's website for example.
Yes, you could achieve water column dosing using dry chemicals.
Some people like to do liquid dosing (or require it for their autodosers, etc); in that case, it is as simple as taking the dry chemicals and dissolving them in the appropriate amount of water.
As for the pricing, for commercial products, you are essentially paying for the cost of shipping (due to the weight of water). You would end up going through commercial products much faster (as they are more dilute). For example, a $4 bucket of dry chemical might last you a year or more (depending on how many aquariums/how large they are, etc)