. . . membership upgraded.

Read the cl-cya page; the correct chlorine level is determined by the CYA level:
http://pool9.net/cl-cya/
With algae, you'll need 20+ ppm. Right now that translates to dark yellow with an orange tint -- to orange on your OTO test kit.

Also, you can NOT operate a DE filter with live algae in the water; it will stop up the filter almost instantly. Kill the algae, first. With very high CYA, you'll need a starting dose of 5 gallons of PLAIN 8% household bleach for each 10,000 gallons in your pool. Repeat those doses till your chlorine mostly survives overnight.

DO NOT try to test with strips or with a DPD color match; neither will give accurate readings with those chlorine levels. OTO is not too accurate, but the results will still be meaningful.