Are you looking at caridinas such as Crystal Red Shrimp or Taiwan Bees, or neocaridinas like cherry shrimp, blue dreams, etc.?
For caridinas, you want buffering substrate with a low pH, and you'll want to use RO water with what we call remineralizer designed for shrimp, like SaltyShrimp GH+. Avoid adding any KH as your substrate will handle stability for you.
For neocaridinas, avoid budgeting substrates. They prefer a slightly alkaline pH (just above 7), and you will want a little KH to go with it. For this, Nilocg GH booster is fine, and most of the time, tap is totally fine for them as long as you've brought GH up to 7-8 or so. If your water is softer than that, add the GH booster.
For buffering substrates, ADA Amazonia is popular, as is Prodobio and SL Aqua. I'd avoid Fluval as the budgeting capacity is much lower than others meaning a substrate replacement sooner than you'll want.