I've got 8 yellow cherry shrimp in a 15 litre heavily planted nano and I find it impossible to see any half the time. It seems because they are a snack in nature they have evolved a strong hiding instinct. If they are anything like my cherry shrimp colony in my bigger tank they will breed and breed before suddenly growing braver in the future. It's also common for shrimp to take a few weeks to settle and with the change in water chemistry they normally shed overnight, so will be somewhere safe hardening up.
My maidenhair really took over and I trimmed off the weaker growth. Unfortunately this made the new growth grow faster in the brighter light where it has shaded the other parts and ruined the shape. I'll be moving soon and I'm going to split it up to try and grow up newer smaller plants.
If your looking for a nice background plant I have what I believe is calathea rufibarba
https://www.houseofplants.co.uk/plants/calathea-rufibarba_velvet-calathea_25740.html which has done really well for me in a lower light situation mixed in with the spathiphillum.