One additional thought - if you go with a river rock type media, you often have lighter color options available. Just don't forget to test it.
A light GB color could help if you are concerned.
The larger your total system capacity, the more stable your temps. Your idea about burying tank and/or sump is a great year 'round stabilizer.
No worries, got to take advantage of everything you can when you live in challenging environments, right?
Hey, being in Houston area, do you get to the ocean much? I previously mentioned river rock, but the stuff I'm using now is actually from the ocean. Has a few small shells in the mix, but overall it works well. Still have to test it though. Mine passes the vinegar test, but I do wonder if the shells do a little buffering...
In the past, I've brought two sizes of screen, a few buckets and sifted it myself for proper size. It's a little bit of work but I like the DIY thing. My rock runs between 5/8" and 3/4" and works well.
Very minimal amounts of shells are ok, I'm sure they do a little buffering for you but as long as they are minimal. I had about 40% of my media as shells at one time. That was NO GOOD. My 300 gallon system is all Quartz type river rock and I can get the pH down in the mid 6 range on that and actually get to buffer up with some potassium bicarbonate (this is actually and exciting good thing to me.) Now I'm replacing my shell mixed media in the big system with an expanded product.
I agree Chip, my well water is hard and I wish it would rain more for me as I can actually get a pH down below 6.5 if I'm not constantly topping up with well water.