GH and TDS is really high!! HELP!!

[ChristinaK]

I have a 10 gallon hex tank that has Fluval substrate on the bottom, a piece of driftwood as the focal piece and it is covered in moss and my plants are all thriving. We let the tank cycle for 3 weeks-month before we brought the water to our local fish guy to test. He said our water looked great and we purchased 4 red cherry shrimp as well as 3 small guppies. The goal is to create a planted nano tank. The fish guy told us to add a small piece of the Wonder Shell to the water to add calcium when we added the shrimp. After we added them, they were good for like 2 weeks and then started to die off one by on. I had no idea why, so I did some research and realized I needed to be on top of the water hardness so I bought testing kits. Ammonia was 0ppm, nitrate and nitrites were both 0ppm, my ph was about 6.5 (which is normal for this substrate), the KH was 54ppm which was decent and the GH was almost 500ppm!! I figured this was the reason for them dying, so I went to the fish store and was told that my water was really hard and I needed to add RO water to the tank to lower the GH, so I did and let it sit for 2 days. The GH came down to about 390ppm so I left it thinking it would continue to decrease....well it didn't, it spiked again....so I removed the remainder of the Wonder Shell because I thought maybe that was the reason why it was still spiking, but after another 2 days, the GH was still really high. KH and all other parameters of the tank have remained the same throughout everything. I decided to test my tap water to see it's levels and the ph is 7 and both the GH and KH were 54ppm, which indicates that the water is soft...

 

SOOOOOOOOO all of my RO water is gone (5 gals) so half the tank is half RO water and half conditioned tap water and I tested the TDS of the tank today with a TDS meter and it read at 400ppm!! How can this be?? My fish are fine, but all of my shrimp are dead. I cannot get the GH down and I am stumped. I thought maybe it was the driftwood making it spike, but my research indicated that driftwood actually softens water..., so that's not it. I thought maybe it was the Fluval substrate, but that is very highly recommended for shrimp tanks, so that's not it. My water testing parameters is perfect, so it isn't that.... and I have not put any chemicals in my tank other than: 1 Wonder Shell, Water Conditioner, an Ammonia reducer sponge and a regular filter pad. The fish food does NOT contain any copper sulfate. I made sure to purchase one with no traces of copper sulfate.

 

PLEASE HELP!!! I am about ready to cry.

[ShrimpsJoy]

I recommend use ro water only. Tap water may have many unknow contamination will get clog in shrimps gills. Drain half and fill up new ro water with out remineralize. Tds will drop down to 200. Slowly add new water, use air line to transfer water will not disturbs shrimps.