Have been on this forum reading for a few weeks (its excellent) but have only got round to posting now.
Am very keen to hear peoples thoughts on a persistent problem I've had in my pool.... long story short, we used to get a pool guy every 4-6 weeks. There was black marks on the pool (algae, but not the actual black spot algae as they all brushed away pretty much completely). He would clean the pool and just brush them away - didn't ever try to get to the source. He's gone and I'm looking after it now (I did years before, and am up to speed on all the chemical types etc). The pics at the end will show it better. All that black is algae, and if I brush it it'll be back the next day in the same spots. This has been there for prob 12-18 months before I'm now actually addressing it.
About two-three weeks ago - I've tried - two courses of 1L Phosphate remover (lanthanum chlorine) which has lowered the Phosphate to about 0.4 (from 1.2 ppm). I've put 1L of a copper based algaecide (40g/L copper) which has seemed to do absolutely nothing - I actually am noticing a few small dark spots that look like copper stains (they definitely werent there before - dammit). Previously I tried dropping granular chlorine (cal hypo) directly onto the bigger patches and let it burn it off with pump off... but again its back in a few days.
During all this time (since starting to address it), the chlorine level has consistently been above 8ppm. What I'm thinking of doing is putting liquid chlorine in to shock it right up to 30+ppm (about 8L for my 9246 gal/35000L pool). But then, how often do I keep adding more and when to stop? My DPD tester only goes to 5ppm and all pool shops around here only measure up to 8 so I wouldn't know above that.
Appreciate anyones help and advice - thanks heaps!
Andrew
