the slime on the shrimp is spounge. it is probably better to jsut leave it in until all levels are good or it disapears
the air bubbles are not produced by diatoms. The bubbles are most likely nitrogen gas. This is a good sign. it means that the anerobic bacteria located in yoru sandbed and other places lacking a lot of oxygen are doing their job of breaking down nitrates and trites into nitrogen gas which then diffuses out of your tank.