The last few years I have put some of my shrimp outside in tubs in the garden. Not this year though - too much else to look after.
It's a really easy and different way to keep your shrimp. No care needed for months! Basically pick a spot that does not get too warm but stille gets enough sun for some algae growth. Actually it is way past the time I normally put the shrimp outside. As soon as it does not freeze at night I have usually put some shrimp in a bucket with tank water and put them outside around mid day and left them until next morning. I still alive, they are put in the tub.
The tubs are set up really simple. Garden soil (without fertilizers, snail poison etc. of course!) and some sticks and branches. I picked some up on the way back from my sons daycare. Top up with some oak or beech leaves and some plants and you're all set. The plants I also collected myself. They can be rinsed from leeches etc. with Potassium Permanganate.
Typical 90 litre tub.
Good plants to collect can be Egeria spp., Fontinalis spp. and Lemna trisulca. I have good experiences with these. Basically any aquatic or semiaquatic plants for ponds or aquaria is OK as long as it can stand the temperature swings.
Fontinalis sp. collected in a nearby pond.
Lemna trisulca - a nice underwater duckweed.
Regarding which shrimp that is suitable for keeping outdoors, the answers is "most of what is readily available in the hobby"! I have mostly kept Neocaridina davidi outside but temperature wise Neocaridina palmata and all the Caridinas from South China are fine for this too.
Neocaridina davidi in different colours that have enjoyed summer outside.
A couple of Topas Blues searching the soil for food.
As mentioned, no shrimp outside this year, but I hope to do more of this in the future. The shrimp that goes inside when the temperature drops in the autumn are really big, strong and colourful and they always breed like maniacs when they get in the warmer water in the tanks.