Even though the "waste water" is considered "dirty" it's much cleaner than your tap water... lol What have I done in the past? Well, I have ran my waste water from my RO Unit through a dual DI unit back to my pure water bin. It does exhaust the DI resins pretty quickly,... and you do have to watch your TDS more often - but that's a pretty good way to keep your water bill down.
Besides,... I run an RO Unit that I run for not only my tanks but also for cooking, cleaning and drinking... and my water bill ... including trash and sewer is about $15 a month.
Also, you don't really have any coralline in your tank. What you are battling is cyanobacteria... which has already been established.
You've been in good hands so far since you have asked me for help. I haven't been ignoring you by any means. This is the first time that I have gotten on an actual computer in the last couple of days. Sorry bud for the late reply.