I've been following this forum off and on for years. It's worked really well for us, for the most part. We've opened our pool three seasons now (skipping last season), and we've only ever had one algae problem, and the guidance here got it cleaned right up.
That said, I have something on the bottom of my pool now. I'm not so sure it's algae. It's kind of brownish, and when it kicks up, it makes the water hazy. It appears to only be on the bottom. It settles mostly on the ends where circulation is less, but has left a pretty even coat of dust across the bottom of the pool, with none in a triangle in front of the return. (whatever it is, it appears to not stick very well under direct current. It just settles.) But my FC consumption is pretty normal. (1 a day or less). Last time I had algae, I seem to be shocked at reading a 0 FC once, so I was immediately suspicious then. This time, if the clarity and the dust on the bottom weren't present, I would suspect nothing was wrong at all.
It could be pollen, based on what I've read here. We do have pine trees around, but I hadn't noticed higher-than-usual activity from them. We usually keep a solar cover on the pool, but it has been open for a few afternoons lately, and stuff can blow in even with the cover on.
here's what I've got:
An Intex 20' x 12' x 48" oval frame pool (about 4500 Gallons). I think it came with a 1500gpm filter pump. I change the filter every few weeks; I changed it last week. I hose it off about once a week if I don't change it. We are in Oregon, not far from Portland.
CYA is about 40.
TA is about 90
pH was last seen at about 7.6. (it tends to drift down -- I just bumped it up with some borax last week when it read 7.2)
I've kept the FC above 3 most or all of the time. Yesterday it was about 4, and that was with nothing added the day before.
I have a TF100 test kit that I bought two seasons ago. I have kept it indoors, out of the sun. When I opened the pool this year, I tested the chemicals on some tapwater, and also on the poolwater as I got TA and CYA where I wanted them. I have opened this pool a couple times before, so I know, using the calculator, what to expect when I add the right amount of CYA, baking soda, bleach, borax, etc. I concluded that the FAS-DPD was not reliable at all. It measured the FC much higher than I knew it to be (2-3x). So, I don't use that test. Everything else in the TF100 seemed to register what I would expect when I opened the pool. The color-block FC test registered 0 on tap-water as expected. With the levels I have, the color block test can tell me pretty well if I'm above 3, so if I see it start to get below 5 (the max of the test) I just bump it back up to 6-7. It seems manageable as long as nothing goes wrong.
This may seem cheap, but it's gotten me a couple months into the season. I plan to get refills next season, at least for the FAS-DPD.
I have added only CYA, Bleach (liquid, 6%), Baking soda, and Borax. (Lately only bleach and borax)
Anyhow, I explain this because what it implies is that I'm not 100% certain of my numbers. But I'm hesitant to go buy test chemicals half way through the season, when I'm still pretty sure these are doing ok, and I haven't seen anything resembling a sharp FC drop regarding this brownish dust problem.
So, once I saw it all settled, I tried vacuuming it up. The included vacuum picked it right up. It was plain to see where I had vacuumed. The pump appeared to spew it right back into the pool, because it was a cloudy mess again by the time I was done. I pulled the filter and hosed it off half way through, and there was a lot of brown int he chamber and a fair amount on the filter, but it hosed off easy enough. But it appears the filter isn't catching everything.
I've heard bad things about Intex stock pump/filters on smaller models, and I read lots about how they're so pleased when they upgrade to a sand filter. So I started looking into that. But after looking closer, I see people mostly complaining about Intex pump/filters being under-powered, not about them being lousy at filtering out cloudy water. I was looking at the Intex 1600 GPH model (About $160), and about to spring on it, but then I read a post where it said that the cartridge filters actually filter better than sand. My problem seems to be I can run this pump all day (usually 8 hrs is enough) and it's not getting the job done... but I don't think it's that it's underpowered... It's just not picking the dust up. The 1600 GPH isn't that much stronger than my stock 1500 GPH... If it's not filtering better either, what's the point?
So... I'm wondering what people think. Would upgrading to a similar-powered sand filter help? Buy some test refills? Something else I should try?
Is it possible to have algae that doesn't quickly kill your FC level?