Newbie to planted - need ideas/advice
Quick intro on experience - had a soft coral saltwater tank for years (120g), multiple freshwater tanks as well. Familiar with all of the basics on freshwater, but nowhere near as knowledgeable as saltwater.
I've been lurking on the forums somewhat passively off and on for months - until now, as I just was lucky enough to inherit a 120 gallon tank from my mother (the same one that ran saltwater for years). I've already decided to go planted - always wanted to, and just begun a fishless cycle. I grabbed some media from the old lady's 30 gal she had as well, and after only a week of initial cycling it's already well along (2x doses of ammonia so far, nitrites are spiking heavily and nitrate already starting to spike). I thought I'd have a month or so easy to research, but looks like my timeline has been bumped up a bit. SO, I'm really hoping for some advice from more experienced keepers (I've done quite a bit of reading so far, so I'm not asking for you guys to get me 100% there in a newb thread). I'll just throw this out in an easy format, and any advice you guys can give/links you can provide/etc. would be vastly helpful.
2'x2'x4', 120g tank w/ dual overflow into 30g sump (originally saltwater setup)
2x return pumps pushing ~800 gph, adjusteable down to ~600 gph if needed
4x 46" lights - currently equipped with 2x 110w full spectrum aquasun VHOs and 2x 110w VHO actinic blue bulbs
Substrate used - top soil w/ a natural gravel top layer from the mom's failed planted setup. She doesn't know what it is, I don't either, but she had researched/had it recommended by a LFS. I know this can heavily impact things, and if you guys think it super important for the health of the tank I can grab pics/etc. under the hopes others will know what it is and what impact it may have. I'm not exactly rich, so I used what was available, after doing some research on the top soil.
Filter media: 2x filter sponges in overflow top pipes, 1x sock media in sump filtering 100% of overflow water (also where established media resides currently)
gH and kH are both looking to be quite high from initial testing - as in at the top of the test strips I inherited. I know these aren't super accurate, and will take for better testing to the LFS or get my own kits for gH and kH.
PH: Out of the faucet it's coming at 8.4-8.6 here. I found a half empty bottle of PH down, and a few doses of that have it closer to 8.0 right now - but I fear having to use too much of this stuff..
So, that's what I have to work with. Now the fun part - I'm hoping YOU all can help me determine the path that will be the most successful for this tank in terms of tank/fish/plant options to pursue, and prepping the tank for them to thrive. I know I would like to do a DIY carbonation following the guidelines for DIY found on this forum (already working with a local homebrew supply to get this rolling) - which I plan on diffusing with a powerhead running on the same timer as the lights directly into the sump. I'm not comfortable with the pressurized option, primarily because I'd like to keep this as natural as possible. Beyond that, I'm really hoping for some solid advice in helping shape the tank, given the limitations I have, into something that will do well long term. Thoughts/advice/opinions on equipment/tank conditions/recommended path to take from here?
Thanks in advance guys, and I'm certain I'll be very active here over the coming weeks/months in trying to swallow as much information as I can chew - I've still got a lot to learn, but I'm hoping I've gotten off to a good start. Looking forward to getting to know this new community!