Cherry Shrimp or Flower Shrimp
If by flower shrimp you mean bamboo shrimp, they require a very strong flow. And they do not eat algae. The "flowers" on their hands are filters that they use to filter particles out of the water which they then eat. This is why they require a strong current, so they can sit and collect food with their fans. They will not eat algae.
Also, you should not plan on having algae. If your tank has nutrients in balance with the lighting and carbon source, you should not get algae. Algae indicates that something is unbalanced.
20 gallon high-tech planted