Black Mold In Hot Tub

[MamaBee]

About a year ago, I had a problem with black mold. First I scrubbed on an algaecide that would take care of brown algae - just to make sure. I think it made things a little better just because I was rubbing the surfaces down. Next, I removed all the fixtures, skimmer door, filter cover, filter lid, and pillows, scrubbed them with a toothbrush with bleach water, and soaked them in a bleach water bucket overnight. I then scrubbed all of the places where the fixtures had been - topside aerator controls, pillow locations. Couldn't do much about the waterfall because I couldn't remove it. But I tried to scrub into it's thin, 6 inch wide spout. Also replaced the spa cover - water had gotten inside it. The new cover that came by mail wasn't built to the Coleman specs I provided so it overlaps on each side by about 3 inches. Also replaced the filter with a new one. I did all of this after I had drained the spa. Then I refilled with residential water, balanced, shocked, and put a Bromine floater in.

Now it's happening again. It starts with little black speckles on the underside of the cover which quickly grow and grow. The underside seam on the cover was filled with this mold. I went away for 6 days and when I got back, it had gone from about 10 pinhead size spots to several dozen that were between 1/16" to 3/8". The bromine level was light, but still there (I had left a floater in while on our trip - there were still a few 1/2" tablets in it.) The water was still balanced when I got home. I have a few spots on 2 of the pillows. It's following the same pattern as before.

Do you have any thoughts on what's going on or what I could try next?

[waterbear]

Post a full set of test results not done with strips for starters. We need numbers to see what might be going on. Also, how often is the tub sed and by how many peolple, how many gallons, how often do you uncover and shock it, What do you use to shock it with? Are you doing one step, two step, or three step bromine?