Can anyone help me with my readings?

Here are my current water readings:
SG = 1.027
Calcium = 500 ppm
KH = 5.8
Alkalinity = 2.06
Nitrates = <approx> 50 ppm

I have a couple questions. My KH and Alk are low. How do I raise those values?
My nitrates are high and continue to be after several water changes, using RO/DI water (and tested before adding). They usually drop down after the change but then shoot back up and hover around the 40 to 60 range - don't usually get much higher than that (if ever). I've tried just about everything I know of - cleaned, changed filters, water changes, less feedings and so on. Only thing I can think of is that I have had about 1 snail being killed or dying about once a week (I have a killer zebra looking hermit crab - who, as soon as I get it up and going, is going in my quarantine tank - had a nasty accident with the last one). I wouldn't assume a single snail that is mostly consumed by the other crabs and shrimp would cause much if any change. The only thing I thought about was removing the bio balls I have, but have heard mixed reviews.
Can anyone help with these 2 questions? Thanks in advance!!

 

Removing the bioballs should help your nitrate readings, assuming you have enough rock and/or sand.


You could always build your own coiled denitrator (a few plans in the DIY section here) if the problem persists.

Here is one of my fave articles on how to correct alk , ca, issues...

http://www.advancedaquarist.com/issues/nov2002/chem.htm

 

ur SG is kinda high u should get it down to around 1.023-24 to do that take out some of ur water and SLOWLY add tank safe fresh water...when i say slowly that is becuase some inverts r very sensitive...ive lost cleaner shrimp that way