The question is...what fish do you keep/planning to keep with your shrimp? There's more chance of the fish eating the shrimp than the shrimp eating the fish.
I hate to say this right after your first post, but please use punctuation in your sentences when posting here. I had to read your post 3 times to even figure out where your sentences start or end and what you are trying to say.
I don't know where you live, but in a shop "algae shrimp", doesn't allways mean algaeeating shrimp.
Here in Denmark a chain of fishshops has sold Macrobrachium lanchesteri as "algae shrimp" for over a year now.