Need help quickly please - Transition to Excel HPT on Sunday!

EDITED: Changed scope. I originally posted in the wrong place, but changed my mind to go without C02 supplementation ...

I am moving this Sunday, and while I have my fish out of the tank, I'd like to go as far as is practical to a low-tech, heavily planted tank.

I've read Walstad's book and have lurked here for a long time, and have been on other fora a lot. I really feel like I'll get the very best advice here so thanks in advance.

I have a small amount of time to shop on Sunday, and about $100 to devote to this. But I live near an amazing and massive freshwater aquarist heaven (Wet Spot, Portland Oregon) so I can get pretty much anything, including Aqua Soil. I don't think they have dry ferts


QUESTIONS:

*I am moving again in 2 months, so I can make more changes then.

What substrate change should I make, if any? I'd prefer not to remove the current substrate, but I could see mixing something in with it or putting it under the existing substrate.

If I don't change the substrate shall I add root tabs? I have Flourish tabs.

What supplements do I need to get this weekend, if any? I can't do any online ordering this week in preparation for the move, I'll be shopping Sunday, so I'm wondering about any commonly available supplements that will be good enough for the non-CO2 dosing.

What else shall I consider?

CURRENT SETUP (I'll post a pic later):

29 Gallon Marineland LED Kit (includes 200gph biowheel filter, and low light LED)
Aquarium Sand with some gravel mixed in, and a lot of Malaysian Trumpet Snails
Aquaclear 35 Power Head for current

WATER & SUPPLEMENTS

My tapwater comes out practically distilled. 0.1 or less degrees GH and KH according to API test tube tests. I use API Stress Coat at water changes, and I add Seachem Equilibrium and API Cichlid Buffer to get GH and KH to 4.

Water parameters tend to be about 5ppm nitrate, zero ammonia and nitrite, ph around 7. Average 30% water change weekly up till now.

FLORA

Some happy crypts, anubias, and java fern

FAUNA

Small danios, tetras, rasboras, pygmy striped loaches, otos, ghost shrimp, and pond and malaysian trumpet snails. 100% stocked according to AquAdvisor

HISTORY

Built in March, fishless cycle in April. Fully stocked by mid-may. Started vaccuming less in May as the snails & such break everything down, nothing really comes out of the sand and I can never see fish poo, just a slightly darker tinge to the top layer of sand.