Freshwater shrimp are great! They have a teeny tiny bioload. You can have as many as 10 per gallon for the smaller types. Many eat algae as well unless they are a filter feeder. There are many many types and colors of freshwater shrimp but I’m just going to cover the more readily available and popular kinds since many have the same care needs.
Red Cherry Shrimp (RCS)
RCS max out at 1.5” and you can keep up to 10 shrimp per gallon. They will eat most kinds of algae, left over food, algae tabs, and shrimp pellets. These guys are a lot of fun to watch but they are small enough that there is always a danger of being eaten by your betta. They breed pretty easily and the females carry eggs under their tails. This is called being “berried” and when the eggs hatch they are miniature versions of their parents and eat the same things their parents do. These shrino usually run $2-$4 each in the pet stores but can be found on ebay for as little as 75 cents per shrimp. The more bright and red a shrimp is the more expensive it will be.
Ghost shrimp are totally transparent and max out at 2”. They eat algae, uneaten fish food, algae tabs, and shrimp pellets. These guys reproduce like rabbits and you can easily tell when the females are berried because the eggs tend to be green. You can keep them in numbers similar to the RCS. While they can be a bit bigger than the RCS they can still be an easy target for your betta.
Japicona Amano Shrimp (Amano Shrimp)
Amano Shrimp are another algae eating shrimp. These guys will not readily reproduce in your freshwater aquarium and it is very hard to raise their offspring who need saltwater to hatch and grow. They max out at two inches and eat algae, uneaten fish food, algae tabs, and shrimp pellets.
Bamboo Shrimp (Wood Shrimp, Singapore Flower Shrimp)
Bamboo Shrimp are very interesting shrimp. They max at 2.5” and are filter feeders. They have fan like appendages on their first six legs that that they wave around to catch food in the water. Once it’s caught in their fans they swipe the fans across their mouth to eat it. I suggest target feeding about three day a week with Hikari first bites using a pipette. This way you know they are getting food and theres no guess work. They also change colors quite rapidly and can be any color from a light tan to dark brown to bright red and any color in between.