We can recommend DYOFIX totally , we use the blue, with the pool being near the river Mersey there's no chance of keeping the weed out, two years ago it was a weekly truck load taken out just to keep it anywhere near sailable, now it's an explosion of growth around May/June, once that's cleared it's just a sack full per week . . .
You need to keep records as you add the treatment . . .We do a full charge every three months and a 5% top up monthly to compensate for rain & bleaching by sunlight .
Blocking the red band light from the bottom is only one food source , 'it' adapt's to consume anything organic , so a quick scoop around to net any floating debris before it sinks is needed a coupla times a week , if you get a prevailing wind everything's usually blown into one corner making it easier . . .
Bill (W M B S )