your lighting needs to be improved, halide or 6-8 bulb t5, leds are better but expensive!
flow! lots of flow, as far as i see theres less than 1000gph flow in the tank.. you need to add some korallias(with a wavemaker if possible to alternate the flow) or get an mp40 on there.
more filtration, just a skimmer and 20g fuge isnt enough.. i would have used a 40g breeder broken down into 3 chambers, 1 for your filter
sock and mechanical filtration(skimmer and atleast a dual reactor for carbon and phosban) 2nd for your fuge area and 3rd fro your return. flow thru that should be atleast 600-900 gph with a mag 12 return so u can throttle it back slightly to match the drainage.
with that said, is your tank a reef ready or do you have a syphen box on it? what type of lighting are you running? looks a bit yellow.., what type of salt do you use and how often do you do water changes? what is your water parameters now? calcium, alk, mag, phos, and how long has your system ben running?
that should give you a big to do list... nothing wrong with what you have but theres always room for improvements right? and if you want coraline u need coraline.. so you should get a piece of rock with some noce purple coraline and stick it in your tank.. keep your parameters up and your lighting strong in a few months youll start to notice small purple/red spots showing up here and there..takes time but it comes..
i know some of this stuff may have been covered but just going over all of it at once..
