Hi and Welcome to TFF from me too!
I would break your sump questions down into two parts: figuring out what, if any, existing media can be re-used and how to go about that, and secondly/simultaneously, figuring out which media types will be both efficient from a biological/mechanical standpoint but also cost effective for you.
I'd have a go at our hardware section "Hardware and DIY" as I've seen plenty of discussions of this type over there. I certainly believe I've seen people use "bioballs" as a freshwater biomedia in sumps as I believe their larger size volume means you are not buying such a large quantity of them as something like ceramic gravel for instance. The top three or four most competitive biomedia types for freshwater are probably ceramic rings, sponges (including coarse "tuffy scrubbing pad" type stuff), ceramic gravels and bioballs. Other substances will certainly be populated by the two species of bacteria but will have either fewer spaces for the biofilms or have other problems.
Another thing that can be helpful in a planted tank situation is the use of additional powered water movement, including some new types that can make broader, less narrow movements, to allow fewer micro-pockets of algae causing ammonia. Our planted tank section has discussions of that.
Unfortunately I agree about the lights probably being too bright, but that too can be discussed both in the planted and hardware sections with likely advice from the experienced folks who frequent those.
Hope this helps!
~~waterdrop~~
