Water Chemistry Makes No Sense

I have been having difficulty with a cherry shrimp tank lately, as the addition of crushed coral made my GH and KH too high. I was trying to exhaust a buffered substrate but it happened sooner than expected and I ended up with a spike in parameters. With a pH of 7.5, KH of 8 and a GH of 11, my TDS averaged 150, which seems very low for a KH and GH that high. Those parameters are the tank's when it had crushed coral in the filtration.

So, I tested my tap water this morning just to get an idea of what my base parameters are and it makes no sense. KH is 6, GH is 7, pH is still 7.5 and TDS is... 87? Why is the TDS so low despite the KH, GH and pH suggesting I have harder water?

My GH and KH are considered too high to be the ideal ranges for cherry shrimp, yet my TDS is only about half of what is considered ideal.

Should I cut my water 50/50 with distilled for a KH and GH of ~3-4 (tank is only 2.75 gallons)? Is there any way to adjust TDS without altering GH?

Note - I am using the API GH and KH kits, as well as a TDS meter.

 

Maybe you should look in to filtered water osmosis.. and buff your water with pH adjuster this want I do for last 15 years.. stay away from tap water and distilled if you start using filtered water to safe on chemicals and no need additional conditioners

 

Maybe you should look in to filtered water osmosis.. and buff your water with pH adjuster this want I do for last 15 years.. stay away from tap water and distilled if you start using filtered water to safe on chemicals and no need additional conditioners

I'm on a natural well, so there's no need for any conditioners.

I don't understand how water can have a high KH and GH but low TDS.

 

I'm on a natural well, so there's no need for any conditioners.

I don't understand how water can have a high KH and GH but low TDS.

I see .. are you using driftwood and real rocks..

 

I see .. are you using driftwood and real rocks..

I don't have any stones in my tanks but they all contain real wood of some kind. I do have crushed coral in the filters but that's because my substrate buffers pH to 6.