Is RDI water worth it??

Hi guys, so for my 55g reef I've always used tap water, with water conditioner, but recently I had a problem with phosphates that effected my hammer corals, which is slow recovering now. Not sure if the two are related but anyway, I was talking to someone to was a lot of experience in the hobby and I was telling him how I have a HOB filter and no protein skimmer and use tap, but he was shocked at how good my reef was doing after only one with those circumstances. Any way he saying how I NEED a protein skimmer like its must-- Ive has water quality issues in the past that the skimmer would have been helpful. Also I NEED to use RDI water and something about the revsere osmosis. I know that this takes all the minerals and chemicals out of tap and its useful and all, but I've came so far without it. But also my reef is not where I want it to be. With phosphate spikes and little issues I can't successfully keep some corals thriving ( hammer corals and toadstools just don't open ) I mean I have luck with my frogspawn and Xenias and Kenya trees, and I see corals growing , I just want to take my tank to next level, ( as far as i can go with T5s, which I heard means no hard coral :bawling: ) Lastly he told me that I should switch to LEDS in a couple years, which I think are cool, but also over priced for a decent set. Any ideas ? Thanks