[low PH with high GH - help]

@ARMYVETthank you very much! I've spent countless hours on the internet researching. You answered my questions only an hour or two after I posted! Many thanks!

[low PH with high GH - help]

I have low kH, low pH and high gH naturally from the tap 30+drops of API gh. (5 gallon) I've amended with crushed coral to the substrate to raise kH and stabilize pH to in and around 7.8. My question is, I'm setting up a new 20 gallon long. I want it heavily planted. I'm planning on Fluval Stratum and root tabs. Can I/should i cap the Fluval with crushed coral? Will this affect plant growth? Can I/ should I/ how do I/ lower gH?

Ok more than 1 question. I'm itching to order my plants. The 5 gallon took 8 1/2 weeks of fishless cycle, due to multiple stalls, (I think due to low pH 6 ( or less) and 0 kH.) Sorry such a long post, but I want lots of plants and not sure if this combo is a good idea.

Also, 5 gallon has 3 Amazon swords and 1 Betta.

Thanks!