Before you make the assumption that your well is/will be low in organics you need to take into consideration the depth of the well, what material the well was drilled through, and how much runoff is from snow melt and rainfall in the direct area versus the water source the well taps into. A well that is only a couple of hundred feet deep, that was drilled through a 20' layer of loam soil and draws from a high water table fed by local runoff has a higher potential for organics than a deep well that is, say, 700' deep (mine is 680' deep), is drilled through 10' of clay soil, sandstone and taps into an aquifer that has a runoff source 100 miles away in the mountains. The latter is representative of the conditions of my well and I have no organics. I have friends and family who live in the Ohio River Valley who have wells similar to the first conditions, and they tend to have some level of organics, often fairly high.
I know someone suggested this in your other thread, but you really need to talk to your real estate broker about seeing well tests and getting all the well specifications. I don't know what the laws are where you are, but a test may be required before the sale of the property. Unless it's a new well, the tests will give you a rough baseline to start working from.
If your well doesn't have any organics, then a TDS meter is even less important. Anything that shows up in the TDS above the general hardness is going to be dissolved minerals like iron, cesium, copper, strontium, etc. You aren't going to mix your well water with your RO water to control these. You're going to mix your well water with your RO water to achieve a certain alkalinity (also referred to as calcium hardness, albeit incorrectly). Those additional minerals have very little if any effect on your buffering capacity. Those additional minerals will be diluted by the same percentage as your alkalinity, regardless of whether you know what their level is or not.
KISS. I believe in your other thread you said yourself you're a KISS kinda guy. A TDS meter may be a nice toy and some may consider it necessary. I know this isn't a popular opinion, but a TDS meter is a luxury. It is not a necessity in any way, shape or form. Personally, I know very few people who keep a TDS meter on hand. Your money is better spent on going the next model higher on an RO system or upgrading your filtration system.
I've lived here for 16 years. My well water is typically pH 8.4 to 8.6, kH 380 to 420 ppm, gH 600 ppm plus. I've kept dozens of Rift Valley cichlids, Central American cichlids, angels, several species of Apistogramma, badis, peacock gudgeons, white cloud mountain minnows, several species of danios and rasboras, keyhole cichlids, kribensis, orange chromides, L-100 bristlenose, common bristlenose, clown plecos, and any number of livebearers, both wild-type and the common domestic mollies, platies, etc. and even had two oscars pair up once, and they all bred in my tanks. Pea puffers spawned but the eggs never hatched. In addition I've kept numerous species of tetras, common plecos, green phantom plecos, red-tailed sternellas, a dozen species of cories, knight gobies, banjo cats, pictus cats, a number of species of Synodontis, several species of eartheaters and probably a few others that I probably don't remember, that all lived happily but never spawned. I've had a little less luck with plants, where I've been limited to species that do well in hard water: ceratophyllum, cabomba, vals, sword plants, crypts, ferns, mosses, onion plants, lilies, water sprites, bolbitis ferns, anubias, one species of rotala, and one species of ludwigia is all I've had luck with. All this has been without a TDS meter, and all of it without even correcting my water conditions. I've used my water straight out of the tap, as is.
If you're going to deal with wild-caught South American cichlids or cats, if you want to breed tetras or cories, if you're going to try to breed delicate, rare loricarids, then you probably do want a TDS meter. If you're into the kind of fish that I'm into, and which it sounds like your into, your money is better spent elsewhere. I'm giving you a no-fluff, honest assessment of what you need, nothing else.
WYite
Your raw water has what you need to keep pH up- the KH. You just have too much of it. That if where the TDS comes in. You get one of those HM TDS meters, some distilled water and some of your raw water. the you put om that old song, Monster Mash. " I was working in my lab late one night......
