oops, I mean phosphates i think and it was only a trace.

The way you kill algae is with Chlorine, algecides are preventative mostly, which Leslie's would love to sell you.

Your problem is your CYA level if its accurate. Higher levels of CYA prevent the chlorine from working. At 100 you will need a huge amount of chlorine to actually shock your pool. That is why you still have algae, even after what you thought was shocking the pool.

I suggest you read this guide, its excellent.

http://www.troublefreepool.com/turning-your-green-swamp-back-into-a-sparkling-oasis-t4147.html

Take a look at this chart for CYA to chlorine ratios.

http://www.troublefreepool.com/chlorine-cya-chart-t2346.html

Do you have a really good pool test kit that can test CYA?
If not test strips will do in a pinch. The only way to lower CYA levels is to drain some water and refill with fresh.

As for your chlorine test, sounds like you have an OTO test that only reads to 5 PPM.

Thats ok, you can work around it by using the pool calculator: http://www.poolcalculator.com/

Read that first link on how to clear a green pool, it will all make sense.

Thanks Goyom,

I've acutally read that in the past. I was getting fustrated with the algae problem way too early in the season for me. I also do the BBB method. But I figured I'd throw the shock in because it was too early in the season. I strayed and shame on me. Leslie's said 100 cya is ok. I should have known better.
I think the algae is gone now. I am still vaccuuming the DE to waste. When I think there is no more, the next day I see what could be DE down at the bottom of the deep end near the main drain. Can you or anyone else tell me what I'm seeing? Is it DE pooling from the sides or is it coming in from the drain?
Thank you again.

your CYA levels are to high
chlorine is locked and not doing its job,thats why its not coming down
drain some water and refill the pool with fresh water
keep CYA levels at between 50 and 80 ppm
get 1 pack of yellow out and throw it in the pool
that will make your chlorine work harder and kill the algae
u probably will have to vac to waste all the dead algae or use a auto cleaner
brush and clean your filter

Thanks Domingos35. I started that process of dumping water and adding fresh. My concern now is the DE. Can it sink to the deep end and pool around the main drain? Or is there some kind of leak at the main drain causing it to come back into the pool?

its probably dead algae
if its DE then u probably have a torn grid