KH and GH question

[Aaron85]

Hey everyone I'm fairly new here, but have had fish when I was growing up. I despised to set up a tank again about 6 months ago. I test weekly and my data seems to be as follows:
Ammonia: 0 - <0.25
Nitrites: 0
Nitrates: 10 - 40 ppm (I usually test before a water change and take out more or less water depending on how high my nitrates are) I believe my nitrates out of the tap are around 10ppm.
I do weekly water changes varying between 10-50%
I currently have an angel fish, 3 silver dollars, and a common pleco. They about 3 inches in sizes, I currently have them in a 29g and plan on upgrading to a 55g in time.
Finally to my question, I test my GH and KH weekly.
My KH is low around 33 ppm 2-3 drops (API test kit)
The GH is higher at 8 drops around 170 ppm I think.
My question is how do I lower my GH while in creasing my KH to keep my ph stable?
I have an aqua clear 50 running peat to help with hardness along with driftwood in the tank. Then my fluval 306 runs purigen instead of carbon. Should I add crushed coral to help increase KH and used distilled water mixed with tap to help decrease my GH.
Any suggestions would be greatly appreciated.

 

[Aaron85]

Here is a picture of my tank.

 

[threnjen]

2-3 drops kH should be enough to keep it stable if you do 50% weekly water changes.

 

[Aaron85]

Awesome thanks for the advise.