My greenhouse is ploycarbonate and I just noticed the roof panels are green with algae. I can't powerhose it as the panels wouldn't withstand that and I can't stand on steps. Any suggestions?
I use a killer spray to put a teaspoon of dish drops to 3 litres of warm water spray over the glasshouse .. green fairy is about the best I've ever come across as it has an oil residue the helps keep muck off the glass inside out .
It also worked with my 30 foot polytunnel .
My greenhouse has 3 mm horticultural glass, it's about four years old & so nice & brittle by now / inside & out .
I do it one section at a time starting off at the top of the roof , spray, leave it for a minute , rub it in with a nice soft sweeping brush . Then horror of horrors .. stand well back & use my 1500 psi power washer to rinse the muck off . So long as you keep the nozzle a good three feet back you're not likely to blow a panel in or out.
Though if that gives you the willy's , just use a hosepipe with a gently spray to rinse things off .
If you've wet it well with the soap spray then left the soap to soak in & agitated the fouling all will be well for rinsing the emulsion of soap & muck off .
Giving the glass a second detergent spray after the first rinse leaves a coating of the washing up liquid spray on the glass , so when you've done the whole roof re rinse it .
It's the same for all sides & the inside.