The first cover came as a package deal with the Pool from American Sales, it was the heavy thick one 16 mil? silver on the bottom, dark blue on top, with "Spaceage" in the name....never saw the bubbles deteriorate other than filling with water over time, probably a result of little pin holes from abuse? Man that sucker was heavy. I have RA and the 5th season I could no longer get the thing off myself.
This one I bought at American Sales in 2007, was the cheapest they had (in stock) and was around $50 or maybe $60 don't recall the brandname, I'm sorry. (Sidenote, my SIL buys the cheapy ones and replaces them every year. She has an 18' AG so her covers only run about $30....
In the last two years my water has changed quite a bit. I did use to run with a routinely low FC because I was using the Pool Frog, and they recommended a FC of 1
. But plenty of times it malfunctioned shooting ridiculous amounts of FC into the pool, off the scale of my then routinely used test strips
. Plus we were brainwashed into "routinely shocking" our pool every other week....
whether it needed it or not....long story.
After the third season I noticed changes with my pool, and for the next 2 summers experienced some problems, which led me to discover TFP in May 2007, the same year I bought this replacment solar cover. So I started that May with CYA over 100 and corresponding FC levels, through 3 partial drains, lowering the CYA to 70 and running with a FC of 5-8 most of the time. Last season my CYA went from 70 to 50 (I did another partial drain at the start of the season) and I lowered my FC level to be around 4-5 most of the time. CYA through dilution and splash out eventually dropped to 20 and my FC was about a 3 for the remainder of the season (late Aug thru Oct when I closed).
Throughout the seasons as I've said I've experienced very high FC from either malfunction of the Frog to shocking for vacation and haven't noticed the bubbles deteriorating like you described.
Sorry for the long-winded report, hope this helps....