yellow green H2O

Been overbusy and just getting at my pool - had to add water to fill about 4 days ago. Treated with pool magnet and algaecide and let filter do it's job before adding any bleach (well water with iron). Started getting a touch cloudy- so tested and added muratic acid to bring my ph down a tad, stabilizer was at 20 so added enough to get it up to 40, and shocked the pool yesterday.

This morning it was perfectly crystal clear, and after church it literally looks like somebody pee'd in my pool. Mainly yellowish/green color. Tested again - here's results:

FC - 5.9 (coming down off shock)
CC - .4
TC - 5+
ph - 7.2-7.3
alk - 137
cya - 40
temp - 72

I have a few leaves and some dirt in the bottom - not too bad. Started my Pool Rover Plus. For now- just gonna let my DE filter do it's job - any suggestions as to what caused it to turn yellowish?? 17,000 gal 18x34 AG vinyl liner. Thanks.

two thoughts come to mind. Copper and Iron. What type of algecide did you put in? If it was copper based and you shocked the pool it is possible that it might have colored the water green. You are using well water with a known iron content. Shocking could cause this water to turn yellowish to brownish.
Yellow and green make yellowish green color. Your low pH is perfect for any metals in your pool to stay in solution and not precipitate out as a stain. The oxidizing action of the shock could then cause them to form colored compounds in the water. I am not saying that this is what happened but it certainly is a possible explanation. The Bioguard Pool Magnet is a phosphonic acid derivative sequestering agent. It is possible that you did not have enough, expecially if the algecide that you added was copper based. It does not REMOVE the metals. It only makes them less likely to precipitate out as stain by keeping them in solution and the effect does wear off in time ( which is why it is necessary to continually redose). I believe it is still possible for them to be oxidized by very high shock levels (Someone with more experience please check me on this last statement....I have heard this as 'pool store info")

Thanks for replying- sorry I'm late in getting back to post results. I think what happened to me this time is that since my water tested 0 iron, I went ahead and shocked it right away instead of slowly bringing up my chlorine level. Unfortunately, I don't know for sure. You wrote that maybe I didn't use enough pool magnet; made me think; possibly I should have used the recommended amount of pool magnet for my whole pool, instead of just for the amount I filled, like the bottle said. It's totally a guessing game.

I went ahead and added more pool magnet, and this morning my pool's crystal sparkling clear! Looks gorgeous. Since I know I pulled that gunk out I backwashed and it came out a yucky brown color. I think it's safe to say that iron was the culprit. Good to go now. Thanks again for your input- you were right on the money.

I only use polyquat 60 algaecide :).