Thank you! My algae is almost gone!

[singingpond]

Okay, I trudged to the pool in the pitch black and redid the CYA test, as you said. The reading is exactly the same. It does not read. Now what?

Do you mean that you diluted one part pool water with two parts tap water (as suggested by Pool Doc), and that the resulting mixture was still so cloudy that the black dot at the bottom of the tube disappeared very quickly -- i.e. with the water level lower than the '100' marking on the tube ? If that's the case, it would mean you have a LOT of CYA in your pool water.

Hopefully you had a decent amount of ambient light for reading the test -- going to the pool 'in the pitch black' doesn't sound promising for reading test results somehow

[auntphibian]

Okay, I redid the CYA test today, diluted and I get 150.

[singingpond]

With a CYA level around 150, you need to run higher chlorine levels (higher than the 1.5 ppm FC you reported in one of your earlier posts). If you look at the best guess chlorine chart:
http://poolsolutions.com/gd/best-gue...e-chart.html#a
the chart indicates everyday levels between 8 and 15 ppm; higher levels for shock. If the 1.5 is typical of the levels you've been maintaining, the algae has had a good opportunity to continue growing in your pool.

I'm pretty much a novice at this pool stuff myself, so take my suggestion with a grain of salt accordingly... If I were you, I would get the chlorine level up to shock levels, turn off your pump for a day or two to let things settle to the bottom, and then vacuum to waste to clean up as much of the settled fine debris as you can (vacuum gently, from outside the pool, not walking around inside the water -- as I think you described in an earlier post). If you have no other way to do this, plumbing-wise, you can just set up your vacuum hose to siphon over the edge of the pool onto the ground. The other benefit to dumping some of your pool water this way is that it gives you the opportunity to bring down your CYA levels somewhat -- by diluting the pool water on refill.

The 'novice' part of the advice has to do with the fact that I know nothing about possible complications from other chemicals/minerals you almost certainly have in your pool, both from the mineral system you mentioned, and from the various pool store chemicals you referred to in your initial post. My own experience is limited to our 1000 gallon 'test tube' size pool, which has had plenty of algae in its lifetime -- prior to my finding this forum -- but no complicated chemical mixes to experiment with

[auntphibian]

I had already vacummed to waste, backwashed and rinsed and added in 5 or 6 inches of fresh water. I will bring the chlorine level back up. It's been raining again, so that's not been easy. We'll give it a shot! I hope Ben is better!