That sounds GREAT Cincinatti! I was hoping for something similar to cross check previous findings.
I have a few comments about things discussed on this thread (what a surprise!!) LOL
My $0.02
Macro Algae will absolutely consume Phosphate. Will it scrub enough to keep up with adding Tap or RO water? Well, that obvuiosly depends on how much is in the Tap or RO water, how much is added through fish food, how much Algae you have, and how well that algae is growing. It will consume a lot but there are finite limits to what it can do. It just seems obvious to me to add as little as possible so not as much needs to be removed.
RO/DI is not a cure all.
The Finger Leather that died in Bob's tank IS a low-light coral and should do fine under the lighting he has. Sorry Bob, but it died from some other cause. I strongly doubt its death had anything to do with tap water either. Leather corals LOVE toxic metals. Have you read my post about Caulerpins?
Not all distilled water has PO4 but you won't know until you test for it.
IMO a high quality 55 gallon reef tank should cost at least $2000. More if you don't DIY equipment.
I have never run a reef system using Plant life as the only filtration. Bob is absolutely correct with this statement. And I doubt I ever will. I fail to comprehend why anyone would choose to completely rely on a single failure point. My current reef system incorporates Algae, Xenia, a DSB, live rock, clams, a skimmer, and water changes. If one of my filtration systems fails I doubt my coral will even notice and I should have plenty of time to fix it before any harm results.
I don't recommend expensive equipment lightly. Anything I recommend I do after weighing the odds of success with or without said equipment. ie. There are many nice tanks without skimmers but a skimmer can give a reef tank just a little bit more room for error. That little bit more can easily be the difference between $1000 worth of corals being merely irritated vs a total tank crash where most new hobbiests just give up.
Just sharing some of my thoughts....