Your Nitrates are at 0 and so is your alkalinity? You're probably ending up with pH fluctuations as well as a cycle then if those strips are accurate, which they usually aren't. I'm not sure if bettas would mind either one, but fancy guppies would probably fare poorly. What's +TH; total hardness?
There are buffering minerals available for those that don't want to mix down with tap water, although I'm unfamiliar with them. Call up your water company if you haven't yet to be sure that they're adding chloramines as well as chlorine, you could be saving yourself a lot of hassle. As I understand it though, chloramine is just ammonia and chlorine bound together; so yes, water dechlorinaters that only remove chlorine will still leave ammonia behind. The ones that remove chloramine, though, convert the ammonia into ammonium which is relatively harmless. I may not be up to date with that info though so will have to look around more to re-verify.
There are buffering minerals available for those that don't want to mix down with tap water, although I'm unfamiliar with them. Call up your water company if you haven't yet to be sure that they're adding chloramines as well as chlorine, you could be saving yourself a lot of hassle. As I understand it though, chloramine is just ammonia and chlorine bound together; so yes, water dechlorinaters that only remove chlorine will still leave ammonia behind. The ones that remove chloramine, though, convert the ammonia into ammonium which is relatively harmless. I may not be up to date with that info though so will have to look around more to re-verify.