I bought a house last year and it came with a hot tub. After I drain and clean it every 3 months - I always get this white/pink residue build up on the sides. It gets especially bad if I try and use "Bright and Clear" from Leisure Time.
My weekly routine aside from balancing pH / Chlorine is:
Hot tub is 500 Gallons
Leisure time Defender : 2 fluid ounces
Leisure time Enzyme: 2 fluid ounces
(When I do use Bright and Clear - It gives me a ton of bubbles with white crap in them. It doesn't matter if I just cleaned it and added new water - or the water is 3 months old.)
Shock it after every use with Leisure time renew tabs which is close to every other day.
Chlorine I do add is Leisure Time Chlorine Granules.
A few times I have over chlorinated the tub to try and kill the "pink slime" but it always comes back so it makes me think its something else.
If there is a better routine I'm all ears please. Would love not to see it any more.