Well hopefully someone with more experience will chime in, but - aside from various pods, BBS, etc. - there are a few relatively easy to breed shrimp species (
Palaemonetes pugio, Palaemonetes vulgaris, Palaemon elegans, and even a few peppermint shrimp species -
Lysmata spp. - to name a few) and - if you can get them spawning - red-ridged clinging crabs/ruby red crabs,
Mithraculus forceps are easy too (green emerald crabs,
Mithraculus sculptus, are just as easy to breed/rear, but they have much lower larval survival rates). Arrow crabs,
Stenorhynchus seticornis, are similarly easy as well, but I don’t remember their survival rates at the moment.
As far as snails go, they range from a bit to a lot more intensive to raise, but stomatella snails, as I understand it, reproduce readily enough in our tanks (most people get them as hitchhikers, but there is a place that sells them - I can’t vouch for them being reputable as I haven’t purchased anything from them and don’t know anyone who has, but they say they offer them*). If you’re willing to spend a bit more, you could try raising
Nassarius reticulatus using SHG’s “Snow Reef” suspension feed or
Cerith spp. using
Oocystis spp. phyto. If you’re up for a bit more effort you could try Florida Fighting Conch,
Strombus alatus, too.
Fair warning, however, to my knowledge, all of these species (except the stomatella snails) produce pelagic/planktonic larvae, so you need to make sure your setup is pelagic larvae safe, or these guys will all die off.
* The stomatella shop:
https://shop.terrareef.com/products/stomatella-snails-3-pack?_pos=1&_sid=70a8ebc41&_ss=rSome relevant links:
https://www.reef2reef.com/threads/b...ns-mediterrane-rock-pool-shrimp-guide.937215/https://www.reef2reef.com/threads/culturing-marine-grass-ghost-shrimp.915793/https://www.reef2reef.com/posts/10632521/https://www.reef2reef.com/posts/10309651/https://www.reef2reef.com/posts/10604072/https://www.reef2reef.com/posts/10655175/https://img1.wsimg.com/blobby/go/38... Catillo Villa Fighting Conch WA Mag 2019.pdfhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2109.2004.01143.x