2 Gallon Tank Lowering pH in a small tank and a GH question

[shrimpshrampshrump]

Hi,

I'm trying to get my tank back into shape so I can get shrimp, specifically Neocaridinas, again (my previous bunch died out, probably from the pipe repairmen leaving the windows open which overheated the tank).
I checked my water parameters and got the following:
pH: 8.4
Ammonia: 0
Nitrite: 0
Nitrate: 0
KH: 125.3ppm
GH: it took 20 drops, which is beyond the chart provided in the kit -- must be more than 214.8ppm

I already have RO in my tank, though I added some tap water so that I can have some copepods and the like. I was told by the fellow at the aquarium that chemicals that lower pH usually require large amounts of water, so I'm not totally sure what to do here as far as pH goes.
As far as GH goes, should I be okay if I do some water changes?

 

[Fishfur]

20 drops is 20 German degrees (20 dGH) and is equivalent to 356ppm.

The only practical way to reduce hardness & pH is to cut the tap water with RO/DI water.

A 50/50 mix would get you a hardness of 10 dGH and a pH likely close to 7 but would reduce KH/Alkalinity to a very low level that might need to be boosted a bit.

One can experiment in a bucket with a measured number of gallons to determine the best ratio of tap to RO.