Ok, let me start by saying I have read a lot of posts on here and this site has helped tremendously.
I have had a pool for years and years and I can take care of the pool water no problem. I just bought an inflatable hot tub at the end of May so about a month ago. I am not sure but I think I may have some biofilm in there already. I have maintained my chemicals correctly I thought. The strips that came with the hot tub measured everything right down the middle. For my pool I use the liquid drops (red & yellow). I decided to check the spa with that the other day just out of curiousity and my ph showed just a little high and my bromine didn't show up at all but it does on the strips. My yellow chemical is from last year, but shows up ok for the pool so I figured it was ok for the spa. Anyway I have some ahh-some cleaner coming in the mail today to give the spa a good cleaning and I guess drain it and refill it and try again.
I have kept my filters changed regularly, ususlly every few days I soak them and then use the pressure washer to clean them off. The biofilm I see looks kind of like a sand in the middle of the pool that keeps showing up. Also use the floater that came with the hot tub for the bromine, holds 1 tablet but seemed ok on the strips. ph and alkalinity and harness all seem ok on the strips too, it is just the liquid test that concerned me.
If I forgot to mention anything let me know, I am still new to dealing with hot water and not cold water.