Sorry to hear of your water and dealer issues. The advice in this thread should help.
Where specific amounts are not given, the owner is expected to read and follow label directions on the specific product used. However, I reviewed our 2006 and 2007 manuals and was not able to find the part you mentioned. I'd appreciate a page number so that I can correct any deficiencies.
You mentioned that your Frontier has ozone. If you have Peak Ozone, please download the manual from
http://www.arcticspas.com/downloads/document_library/PeakOzoneGuide.pdf).
In extreme cases of sources of water with high minerals (such as some well water), we recommend that you add add 1 tablespoon (14 grams or 15 mL) per 1000 litres (265 gallons) of Arctic Pure Best Defense weekly. Your dealer should stock Arctic Pure products which are recommended for use with our spas.
BTW, Baquaspa is known to cause maintenance problems (damage to some plastic components, most notably the light lens, in pre-2007 models) with our spas. If you have an affected model, your dealer should now have biguanide-safe replacement parts.
That being said, many Arctic owners report success with biguanide systems (though apparently there is a 'goo' problem after two or three years) and you are welcome to try it.
Best wishes
Tom