Using RO/DI water

Coming fresh out of the Reef hobby and getting back in to Discus I am sure you could imagine I have on hell of a RO/DI unit. After reading a bunch on freshwater tanks in the past couple days I have come to understand that I can’t use pure RO/DI water by itself. I will either have to re- mineralize it or mix in tap water.
I live somewhat in the country. I have not checked my water chemistry yet but I think my water is very high in minerals with an avg 320tds before it goes in to the unit and as the water sits in my toilet bowls I get a black ring around the bowl. Plus I do know the water is high in CO2 as I go through DI resin quickly. Have 2x 60 gallon holding tanks.
What is everyone’s suggestions on how I should prepare my water?

320ppm isn't bad at all. I've kept wild hypancistrus and peckoltia for extended periods in 460ppm with no problems. Definitely age/agitate the new water. It should only take a few hours if you use a pump, longer for airstones. I don't bother heating new water if the temperature is within 10F, but a lot of people prefer to heat it.

If you feel strongly about using RO, you can ditch the DI unless there's something specific you're trying to remove. The 10-20 increase in TDS just isn't a big deal in this case.

I’m not dead set on using ro water. If I can eliminate and simplify things for me I’m all in. When you say “age the water” what are yo referring to? is ther any kind of buffers or additives that should be added to the water?
So use regular old tap water for such a beautiful fish?
Of course I know I have to dechlorinate the water

My meter is dead, but I believe my TDS is in the 420 range and my discus do great in this water. I only use RO for breeding and then mix in tap beginning just a couple of days after hatching. No other additives are needed.

Aging the water means to fill a storage tank and use an air stone or circulating pump to off-gas the Co2 and stabilize ph then pump it into your main tank during water changes. If you have chloramines in your water, an additive such as Prime will instantly break the chlorine-ammonia bond.

By age, I mean letting the pH stabilize. Pumps/vigorous agitation speed up this process. My 55 gallon barrels take about 3 hours with a 950 gph pump attached to a 10' hose. I clamp the hose to the barrel so the water splashes as it returns.

I think the black ring is either manganese or iron. I don't think either will cause significant problems with discus. Stability and consistency is more important than hitting a specific number. If RO helps you get the stability and consistency you need then why not use it?

The water in San Angelo Texas is 1120 TDS out of the tap. I run it through an RO/DI system, gets it down to between 2 and 6 TDS. I do 50% water changes using approximately 1/3 Tap water. I check to TDS as I refill the tank and try to keep the tank at 150 TDS. I also add Seachem Discus Trace. Seems to be doing ok. Any thoughts would be appreciated. I am also running a Fluval FX4 and Fluval 406 on the 75 Gallon tank with approximately twelve pounds of biohome ultimate.

DI is probably not really worth the added expense if you're reconstituting with tap or waste water anyway. When I used DI the resin cartridge exhausted pretty quickly. RO alone would most likely bring you down to the 10-20 TDS range.

My TDS in KC hovers at 500 and my discus are fine. I only use RO for breeders...

320 tds is no problem at all, the water at my last house was like liquid concrete and came out of the tap at 750 tds (not as high as robcope's though!). I simply used a HMA filter to remove any nasties in the water and they were fine. If you don't want to buy a HMA, putting your RO unit in flush mode to bypass the membrane would have a similar effect, that is, it would go through a particulate and then a carbon filter.

Like Adam said, ageing the water is just heating it, oxygenating it and letting the ph stabilise nothing more, depending how you do it it can take anything from a couple of hours up to 24 hours, the more agitation it has the faster it ages.

You'll get much better results by making large, frequent water changes. Your discus can grow, thrive and breed under the conditions described. A reef tank is completely the opposite of a discus tank. Most of us keep discus in barebottom tanks with a sponge filter and a heater. Feed heavily and clean out the tank afterwards. No special equipment needed at all. Unlike reef tanks, discus keepers put all the $$ into high quality fish.

Good luck, Willie