Response is much appreciated polishpollack. Hereby nominate you for President of the DWC fan club. May consider a method change but not likely. No light is getting through to 40 gallon reservoir and there is no sign of algae there. When reset, all components get thorough bleach solution/rinse/dry. Tubing and pumps are cleaned and have also been replaced. Running a second pump to circulate water along with air pumped into a stone as well. Using jumbo pots has reduced sites from 28 to 24 but better blocks light to tray. The only sign of algae is the at fill/drain area of tray. I will get some panda liner to cover that spot to see if it makes any difference.