The camel shrimp will end up eating your SPS. I would recommend that you get a skimmer before attempting SPS. I have a friend who is keeping his SPS without the skimmer but his tank had been stable for years and has a very large water volume of above 500 gallons. He employs other form of nutrient export like a refugium with chaetomorpha algae and mangroves. Currently as I see it if there are no means of nutrient export and you do not engage in frequent water changes to keep nutrient levels low, all you will end up with is brown sps.