The first question:
Protein skimmer take excess waste from the tank. Without them, waste floats around the tank and causes increased phosphates. It is well known that phosphates will cause decreased coral growth and at high levels, cause stress in more sensitive corals
Second Question:
With that being known (about the skimmers and phosphates), goniopora is VERY sensetive to high phosphates and comes from pristine waters. Nutrients and different then what you think. Goniopora needs the same quality food your fish do. You wouldn't feed your fish detritus that's floating around in the tank right? Also, the main things your goniopora need are correct lighting (which yours looks very bleached so it's either getting too much light or is highly stressed or both) to photosynthesize, calcium (around 440), Alk (around 9), and magnesium (around 1440). Those are the "nutrients" your corals need, not dirty water.
Thanks for the advice....I knowbthe guy looks bleached but my camera phone does horrible justice. I couldn't get it to snap as bright green like it really is. I just may get a skimmer im just worried I will over skim stuff and not know how much food to put in. I use phytoplex, micrivert...and feed fish a mix of saltwater cuisine frozen food and cyclops...any food suggestions? I also do water changes ever two weeks. 10 gallons..is that enough? I use r/o for sure...tap is terrible here in texas.