I really appreciate everyone's replies. @talontsiawd
, should I take this to mean that the higher the tap water TDS reading, the more it should be diluted with R.O. water when doing water changes? Also, can you recommend the specific TDS meter you got for $20? I think I'm going to buy one and put it in my hubby's X-mas stocking, but there are so many models out there and at all price points. I'm not looking to buy top of the line but would hope to get a reliable one. Thank you for your in-depth reply, now at least I think I have a basic understanding of TDS meters and their purpose/necessity.
Please know that I just got one so I am no expert. Check the shrimp forums for brands but I was recommended this on Amazon: HM Digital TDS-3 Handheld TDS Meter With Carrying Case, 0 - 9990 ppm TDS Measurement Range, 1 ppm Resolution, +/- 2% Readout Accuracy
That was recommend for under $20. Is it good, I don't know, but seems to follow what I do, but I haven't even had it for 30 days, I can still return it.
As for the first part, I would say if you want lower TDS, and you have high TDS out the tap, yes, it would make perfect sense to use more RO water. If your RO water is like 3-10, and your tap is 500, then you could do 50/50 and get 250, or whatever makes sense.
For more specifics, I am not the one to answer questions, yet, I don't know enough. I currently EI dose and it seems that can raise the TDS 100-150 before the weekly water change. That is just what I read here. Since that is what I do, I give a range of about 250 before I do a water change, or weekly, whichever comes first. I am experiment as I have a not so common deficiency that I am trying to figure out. Point being, most people use it as a basic assessment or guideline, not scientific, just a bit of information to consider.
I still recommend picking one up, I think it is a great gift idea at the least, but I actually like mine way more than I thought. My water is inconsistent too, that alone helps me. But I had a 14x increase than my tap, I saw a big difference getting it down to 3x as much. I wouldn't have known with any test kit I use, and I don't test my water daily, I test my TDS daily or more, because it is so easy to do. I would check the shrimp forum on the search, it is really important with sensitive shrimp and breading it seems.