How big is your tank? I can see problems with your current stocking now that I think need addressing.
If your pleco is a common pleco (they and bristlenose seem to be the most regularly sold plecos) it is going to grow to over a foot long and even at smaller sizes it produces an extraordinary amount of waste. A fully grown adult with need an extremely large tank.
Zebra fish (assuming zebra danio) are schooling fish. You should have at least six individuals. They are also extremely active fish and so are usually recommended for tanks 20 gallons and up.
Rainbow sharks get quite large and can become aggressive/territorial as they grow. Seriouslyfish is saying a tank with base dimensions of 120 x 45cm as minimum for keeping this species.
If he won't eat the shrimp, you are going to need to provide it with a pelleted food. I probably wouldn't want to encourage hunting behaviour in case it starts harassing the other fish in your tank.
Edit: Okay I was posting while you were replying. 10 gallons way too small for the stock you have.