Advice on tap water

After 20 years considering returning to keeping discus. I have a very nice 90 gallon corner with a wet-dry system, currently in storage after the last fancy goldfish passed. Just bought a 37 gallon (will become the holding tank once the 90 is back up) to ease my way back into the more serious end of the hobby with some Cardinals and bristlenose to warm up the tanks (after fish-less cycling of course). Just ran some tests on my tap water. It is very soft NW Oregon water and I know the city adds to it to get the pH up.
pH 7.4 (this is stable in my daughters 10 gallon Glofish tank)
KH 17.9-35.8
GH 17.9-35.8
Ammonia 0
Nitrite 0
Nitrate 0 (city quotes online 0.1-0.5 ppm year round)

Is this water OK? Do I need to add anything for the combo discus/cardinal/pleco? I intend to keep some driftwood in the tank and maybe a decoration or two but planning on bare bottom tank for a while, no plants.

Hi Bill,

What's with your KH and GH readings? In ppm TDS, that's roughly 300 to 600.

Just throwing this out there too, the goal of a fishless cycle is to create a stable environment with as few pathogens as possible. Add the expensive fish first, let them settle and then contemplate adding the cheap stuff. Not worth killing a discus for a cardinal or ancistrus.

Sorry should have been more specific, those readings are 17.9-35.8 ppm or 1-2 dGH and dKH. I actually think the GH is closer to 1 dGH as the color is between with one drop.

These will not be back-to-back adds. The 90 gallon is out of commission probably till summer so it'll be cardinal/pleco only for a good long while in the 37, then I move them to the 90 and the 37 will be refreshed for observation of any new adds. I love my 90 tank but it is not a good treatment tank.

Wow, that's an apisto breeder's dream. You probably need to buffer it a bit but hopefully someone else can chime in. My water is on the opposite end of the spectrum, 450-500 ppm.

Its nice, soft water. Whether you need some buffer depends on how often you change water, and the size of the bioload. You can watch what the pH does between water changes, and if it falls too much a handful of crushed coral in the filter should keep it stable enough. My KH is less than 1 degree and I only use buffer on tanks that get less frequent WCs.

Another way is to move the group of discus straight into the 90g after a fishless cycle and consider that the quarantine. That way you can cycle it ahead of time to a strength where its ready for the whole group, and avoid the inevitable mini-cycle that happens when the filter is only handling a few tankmates.

Great water for discus,similar to my water here in Halifax,Nova Scotia.