I'm using RO because that's what my boss wants me to use... we sell a lot of it at the store, especially for people with well water, so it's best if I don't rock that boat too much.
It's not straight RO; I use about 15% tapwater to bring the RO up to temperature, so it's not completely sterile. KH also varies a lot out of the tap at the store, so it's nice to keep it predictable. I wouldn't mind using straight tapwater like I do at home, but I'm trying to play by the rules.
I'm using Flourish, usually about 10mL, three or four times a week.
I'm almost completely sure Seachem endorses the use of both Acid and Alkaline buffer with RO to get the KH at a stable level... I remember my manager telling me that they told him the ratio that we recommend at the store. When I mix them, the KH stays stable for way longer than just the use of Alkaline buffer. I keep the KH at 4 dH, GH at 6, CO2 concentration at about 25 ppm.
I think I'm giving you guys the wrong idea about this tank... it's going well, I was just surprised to see the plants slow a bit. There's absolutely no hair algae and the plants are pearling like crazy. I have a couple "Riccia toupees" on the top of the driftwood I forgot to mention and they're having some fun about three hours after the lights turn on in the morning and stay covered in bubbles all day long. The lotuses are sending up streams of bubbles in several places, as well. I was worried because the Myriophyllum only grows after water changes and the hairgrass hasn't filled in much lately.
A few days ago, I added about 3mL of Flourish Phosphorous to the tank after my usual 50% water change. The plants looked even more vivid than usual the next day and of course had that growth spurt they always do... I added more PO4 the next day and my NO3 levels actually went down by 4 ppm. I'm going to continue the PO4 in small amounts, according to how quickly the tank eats NO3, and make sure I keep up on Flourish addition, in case the plants are hungry for trace elements. With that big jump in NO3, however, I'm thinking it's a phosphate issue.
I guess my questions are more of a quest for nutrition info than a "help me because the tank looks like heck" post, but thanks for all the replies anyway... this is a pretty cool discussion.
My boss told me that he has a bunch of articles that our Seachem rep sent us (probably the same ones on their website, actually) Once I have time to read those, I'll let you guys know if there's anything pertaining to the questions we've raised here.