A little update:
The archer (Spitfire) has been doing well. He eats pretty well, and I feed him around 2-3 times a day, depending on how long I'm gone in the day. Should I try to feed him live bugs or are bloodworms just fine? I just cleaned his tank yesterday so he's extra happy with clean water and fewer plants. A really cool thing about the Anacharis is that roots are dropping down from the "stalk" (not sure what you call it, I'm brain dead right now) and it creates this almost mystical look. I'll take a picture soon and post it.
In the future, I intend to keep the Anacharis in the tiny tank (didn't work out in the main tank, I put a few in there and they were just annihilated, maybe by the flow? idk), however, I also intend to get some Marimo Moss balls or some fuzzy moss (mainly for the shrimp).
Are there any other shrimp decor recommendations? I've seen these mineral balls for shrimp before at stores, do I need them or not?
I used to feed archers crickets pretty frequently; rarely got any to spit water, but they had no problems trying to jump at the insect. Would sometimes forget that I left a bag of crickets on the tank lid and come back to an odd banging noise that turned out to be the fish repeatedly bashing themselves into the lid, trying to get the insects in the bag.
If gut loaded, they'd probably be a bit more nutrient-dense than the bloodworms; and archers would usually be far more inclined to eat them when offered IME.
Keeping shrimp is heavily reliant on your water parameters, particularly your TDS, gH, kH, and pH. Those "mineral blocks" are somewhat significant if your parameters aren't decent (but are generally useless anyways IMO). You can't keep caridina (cantonensis, serrata, etc) without low, almost zero kH, low pH, and moderate gH, otherwise they encounter multiple issues with osmoregulation, moulting, fertility, etc. Neocaridina davidi/heteropoda. require somewhat low kH, neutral pH, and moderate-somewhat high gH, and can die if kept in optimal 'caridina parameters' or exceptionally hard water; though because they tend to prefer more of a "middle ground" between acidic and alkaline/soft and hard water, they tolerate a wider range of parameters and are less prone to death due to parameter issues.
I personally don't really have much in my shrimp tanks; a decent aquasoil substrate, some miscellaneous ceramic structure, a clear glass feeding dish, some wood, dead leaves, a sponge filter, and maybe a few plants that I'm trying not to kill, plus high light.
You can add pretty much whatever you'd like, so long as it remains fairly chemically inert and is non-toxic. Plants help with parameter stability and provide cover for females and young shrimp; wood promotes growth of edible microorganisms, which shrimp are rather fond of; etc. Plastic decor works, too, so long as it doesn't disintegrate over time.
Plants I typically add to shrimp tanks include Cryptocoryne spp., Bucephalandra spp., Anubias spp., misc. mosses, some stem plants, etc.