First, don't bother to test NitrAte until your Ammonia and NitrIte are 0. Most NitrAte kits convert NitrAte to NitrIte and then measure, so your NitrAte reading will be way high if you have any NitrIte present.
Second, I would say yes, an RO
system is a must, I can't tell you how well using RO
water solved algae and Cyano
problems in the tanks I work on. I got mine off eBay (purewaterclub, I believe, was the seller), I got a 150 GPD w/dual DI
for $114 shipped, then I got a TDS
meter to test the output water on occasion. I just connected mine directly to the cold water line after the softener in the basement, and then only turn it on to fill a 44G BRUTE trash can, where I then heat and mix salt a day or two before any PWCs. For your uses, a 50 GPD system and a 20 G trash can would work.
You could also hook up the system for home drinking water use, and get a holding tank so you always have a drinking water supply. However, I will let you know that the TDS
of water going into the holding tank will increase as the tank fills, so you don't want to use that for your tank, even after running it through the DI
(which will go to fast anyways, and burn out your resin).
This is something I came across, and I confirmed it in discussion with someone working with RO
systems for 20 years. I noticed something strange when I was testing my RO
water (before the DI
- I installed a tee and a tap valve) that when I first started it flowing, the TDS
would start at 150-200, and then slowly ramp down to below 20. When your RO
membrane is not producing, it allows more time for the concentrated contaminants to cross over the membrane, whereas they would not have enough time during production.
Also what happens when you are filling a pressure tank is that as the pressure tank fills, the backpressure increases and for some reason, this also allows more ions to cross over. It didn't make much sense to me at first, but it's some kind of physics thingamabob that I can't remember at this time. This is really only the case where you have a flow limiter on the discharge line. Those are added to these systems to achieve a better discharge to filtered ratio (1.25:1 for mine, I think). If there is no flow limiter, you end up with something like 20:1 so it's a give and take.
Sorry for the dissertation. I'm bored today.
Oh yeah - don't drink DI
water, only the RO
water is really, really bad for you.