I have a frustrating greenish cloudy water problem. Sorry for the long post; but I'll give as much background information as I can in case any of it is relevant.

The pool hasn't been clear since it has been opened (over 3 weeks now).

I have a 13,500 gal fiberglass pool, Sta-Rite sand filter - model T-200BP-1.

I live in Wisconsin and have a mesh winter cover.

We had an unusually hot spell (> 90 degrees) in April, at least 3 weeks before the pool was opened...no suprise, when the pool was opened, it was thick with green algae. (Lesson learned - need to open earlier if this happens in the future).

When the pool was opened, I had the pool service company replace the sand in the sand filter (Lesson learned - this probably wasn't necessary for a 3 1/2 year old sand filter).

I spent over a week maintaining slightly higher than normal sanitizer using liquid shock, but mostly trying to clear up the algae with algaecide (poly 60)...I wasn't making any significant progress, and started reviewing this forum for tips. (Another lesson learned - need to attack the algae with chlorine first)

I switched to maintining very high sanitizer levels using liquid shock, and this seemed to have a good effect. It **seems** that the algae is killed, and I've since scrubed off the algae from all pool surfaces and vacuumed it out.

However, I was still left with slightly green, cloudy water. My next step was to use clarifier - I suspected that my new sand wasn't as efficient at removing particles as my old sand...This seemed to help somewhat, but I still couldn't see the bottom of the pool clearly.

My next step was to drain approx 1/3 of the pool and refill with (private well) water.

After a couple of days since the refill, still have the same cloudy water.

I am entertaining a suspicion that the pool service company possibly messed up my filter when they replaced the sand. However, there is no sand in the bottom of the pool, so I don't think there is a broken lateral.

I have been not backwashing the filter because I've read that too frequent backwashing of a filter can cause problems (channeling?), and my pressure hasn't been rising at all. The lack of pressure rise seems strange to me.

This morning, I reviewed the manual for the filter- it says to backwash daily when opening the pool until it is "sparkling clear"...I just backwashed this morning, and plan to backwash daily unless I get different advice from this forum.

Here are my test results from the PS233 testkit:
FC 12.5
CC 1
TC looks like slightly greater than 5 (the max of the readout)
pH 7.5
Alk 190 (was approx 120 before refill with my well water)
Cya 60

Any advice would be greatly appreciated. Thank you.