Just for clarification the abbreviation is RCS - Red Cherry Shrimp.
CRS is for Crystal Red Shrimp.
Annoying and confusing I know. The only reason I point it out is that if you are asking for advice or information on keeping them it WILL make a difference which type you are keeping. People have had great success keeping Red Cherry Shrimp in these types of bowls and getting them to thrive (breed and maintain good health). With Crystal Red Shrimp things seem to be more difficult/high maintaince according to the reports that people have made here who attempted it.
The combination of low waste production and very minimal oxygen requirements (along with general hardiness) allow the Red Cherry Shrimp to thrive in these bowls with very little effort even when not using any sort of filter, aeration or heater. Other stocking options (Crystal Red Shrimp, nano-fish) seem to really push the limits of what these bowls can 'naturally' filter and balance and might require mechanical assistance (filters, etc.).
Red Cherry Shrimp like you have will be fine in the bowl as long as you have enough plant matter in there to soak up the small amount of waste that they produce. If you feed the shrimp that will actually have more of an impact upon water quality than the entire shrimp population most likely so just be careful to use very small portions if you feed them (and skipping days might not be a horrible idea if you only have three shrimp). I don't know what the ratio is but they seem to consume WAY less food than even the smallest fish.
With established plants (and especially if you have rock or wood in there that develops bio-film and/or algae the shrimp will actually be able to forage for most of their food.