So I recently set up a 2.5 gallon tank I'm intending to use for crystal reds. It is a planted Walstad style tank with a gravel cap. I currently have some pearl weed, dwarf water lettuce, and some java moss that may or may not be dead. Also a piece of spider wood and a couple pieces of dragon stone.

The tank is currently cycling and ammonia/nitrite are both at .25ppm. pH is around 6.8 and temperature is about 70.

Over the weekend I received my salty shrimp gh and my tds meter so I went ahead and remineralized some distilled water. My tds in the tank was at 178. I just received my gh kit today and at first, the water read a gh of 10. I emptied about half of the tank and replaced with distilled water. The tds came out to 108 and the gh came out to 7. I know I'm aiming for a 5, but I feel like in order to get there I'd need to drop my tds way too low.

Could my test be faulty? Could something in my tank be messing up the gh reading? Is it safe for me to drop the tds lower to get a gh of 5? When doing the gh test, 1 drop = 1gh correct? Just want to make sure I'm understanding the test correctly as well.