orinokai

I have just purchased a wood fired hot tub and have been researching the myriad ways of treating the water! I'm quite keen to keep the water as natural as possible because of eczema in the family. I only intend on using the tub infrequently... maybe once every 2-4 weeks... and the water would be cold when not in use (I'm in a maritime climate on the coast of the UK). I haven't seen many folks talk about simply draining and refilling the tub before each use. Would that be an option or would mould or algae become too much of a problem? If so, would a weekly shock with hydrogen peroxide be sufficient to keep mould and algae from forming? Thanks for any advice!