yeah thats aiptasia your lucky you only have some i just wiped out 300 heads in my 33g using a filefish.right now where your still cycling your left with manual removal so injecting them is best either with a kalk paste or lemon juice these methods are only good in small numbers once you hit plaque status like i was theres hundreds of baby heads youll never even see and youll need somthing that eats them like peps,nudis,filefish,copperbands etc.
take a look at my zoa tank and browse through the pics and see what aiptasia can get like if you leave it untreated and take a look now not a head to be found and things are way healthier.
your liverock is your main source of filtration your skimmer takes out the stuff your liverock couldnt process and also areates your tank for oxygen, i dont use a skimmer on my 33 because the bi load is small and my liverock is plenty on the other side if i had more livestock i would need more room thus removing rock and needing something to help keep the balance...a skimmer is the perfect candidate.
lots of liverock and a huge powerful skimmer are a force to be reckoned with and allows people to increase their bio load by a great deal.
remove your foam is a great suggestion i dont think your bubble trap will work properly with it in so tight and no ever cleans them as often as they should plus in my opinion if it aint a filter sock(which gets taken out also and cleaned reguraly) then no fabric should hit your tank.if you do keep anything in the tank that will absorb waste be sure to keep it cleaned or exchanged reguarly.
your getting alot of bubbles in your sump is it from your drains?? or skimmer??