mold at liner and rim seam and other questions

Three items
1) my pool has a power cover and is covered unless going to be used for the day. Complete rebuild of pool 2016.

Thin line of mold (1/2 inch wide) at the bead of the liner is building around the entire pool. Thinking either a vinegar or diluted chlorine solution sprayed along the line will clear it.

Thoughts?

2) I don't typically "shock" the pool... I maintain (recall very low CYA) CL levels between 0.5 (high sun days, and 4 ppm. (roughly a 1 gal bottle of 12.5% pool chlorine). On average pool uses .5 bottle per day. Ran across articles around Crypto spores resilience to chlorine and wondering if I should start a periodic shock regimen from a safety perspective?

Thoughts?

3) Low to no CYA in a covered pool. Value in bumping this up? Historically run through roughly 70 gallons of 12.5% per season including open and close. (Pool has always opened clear but ready to go green as soon as exposed to light and heat. Have always had residual chlorine prior to opening from previous season closure.

thoughts?


Ohio (Season typically 1 Wk before Mem wknd to 1 wk after Lbr day)
In ground 18x36 26,000 Gal
1hp Hayward Super Pump
DE filter BBB method
k-2006 Taylor
Balanced
Religious monitoring of chlorine
very low CYA
240K BTU heater for spring Start up, fall extension
Coverstar power cover
Pool will solar heat to about 92 deg if covered at peak Summer.