Considering getting a small tank (I think it's about 20L but I haven't gotten around to taking a look at it) and stocking shrimp in there. Will it be big enough? Also can you house ghost and cherry together or just one species (I'm assuming for that size just one)?
How many could I get? I don't really want anything bigger for them as I'm strapped for tanks as it is lol.
I have cherry shrimp in a 30 litre nano cube which is perfect so 20 litres should be fine too. If you want a tank which is designed for housing shrimp then take a look at the Fluval Ebi shrimp tanks, its a kit which you can pick up for about £85.
Ghost shrimp and cherry shrimp won't interbreed, but I've read mixed reports about ghost shrimp being too aggressive to keep with smaller shrimp. I can't say for sure how it would work out because I have never tried it. I DO, however, have an amano shrimp and orange sunkist shrimp in with my yellows (which are the same as cherries but a different colour). The amano is at least 4 times the size of the yellows, and the oranges are quickly getting up there in size themselves. However, they are not aggressive and are a great way to add some more colour into your tank.
That's a long way of saying that I'd recommend keeping something like orange sunkist shrimp together with cherries, rather than ghosts with cherries. Ghosts are also a lot more plain, so if you're happy with a see-through shrimp then I'd recommend amanos instead and then at least they will eat your algae.
ALSO, I bought a Fluval Ebi and, while I thought the tank itself was quite nice (and my shrimp loved climbing around the 3D background), I found that the Fluval Statrum substrate was very, very messy; I rinsed it carefully but throughly, as per the instructions on the bag, but it still took days for it to settle and my water to be clear, even with my filter full of polywool. Later on, any aquascaping that I did also resulted in large brown clouds and you can't syphon it like gravel. The dust from the substrate would land all over my plants. I also don't like that the filter is internal and gets messy very fast (probably because of the substrate). I ended up switching all of my inhabitants over to my 20 gallon with normal gravel and a better filter. The tank was seeded with my old fluval filter and all of the good bacteria from things like the driftwood, plants, and moss balls, so I didn't have any noticeable cycle and was able to move everyone over very quickly. I now plan on taking out the stratum, replacing it with gravel, and getting a small sponge filter or external filter and just putting a betta fish in it. I think you could get a similar shaped, nice looking tank, with better equipment, for cheaper.
ETA: I think that a 20litre tank is big enough for a decent colony of shrimp, but I might just stick to the cherries at that size. You want to have lots of them so you can see them interact normally. If you had a heavily planted 20L, I think you could have quite a few cherries in it. If you went a bit bigger, I'd still recommend adding some orange sunkist or something like that.
Love the idea, Of getting a little one with some shrimps & A small group of Cardinals. They look so beautiful 
