This is just an observation of mine relating to having a darker liner and how it effects the pool temperature. Hopefully it is helpful to someone else in the future when trying to decide. When I was researching this during our pool build the opinions I found were that the effects of a darker liner heating the pool was marginal.
Before my current pool pictured below I owned an above ground 15x30 with a pretty standard blue liner. When we decided to build a new pool at our new house we really liked the looks of a dark liner and wondered if it would help with heating the pool as well. I can say that based on my non-scientific observations of temperatures over the past year it does appear to make a noticeable difference. Within the first week of filling it last year in July the temperature shot up to 84 degrees without using a solar cover. That is in Michigan. I never saw such a sharp increase in temperature with our above ground in the 3 years we had it and I don't think I had many days, if any, where the temperature was above 82 even with a solar cover. Another observation I had today while swimming was when it was sunny and I ran my hand over the liner underwater I could feel the warmth radiating off of it.
Correct me if my logic on this is wrong about this, but the unfortunate part I noticed is that it does seem like it is much easier for an algae bloom to take hold starting at the walls and floor because of the higher localized water temps near the liner.

Before my current pool pictured below I owned an above ground 15x30 with a pretty standard blue liner. When we decided to build a new pool at our new house we really liked the looks of a dark liner and wondered if it would help with heating the pool as well. I can say that based on my non-scientific observations of temperatures over the past year it does appear to make a noticeable difference. Within the first week of filling it last year in July the temperature shot up to 84 degrees without using a solar cover. That is in Michigan. I never saw such a sharp increase in temperature with our above ground in the 3 years we had it and I don't think I had many days, if any, where the temperature was above 82 even with a solar cover. Another observation I had today while swimming was when it was sunny and I ran my hand over the liner underwater I could feel the warmth radiating off of it.
Correct me if my logic on this is wrong about this, but the unfortunate part I noticed is that it does seem like it is much easier for an algae bloom to take hold starting at the walls and floor because of the higher localized water temps near the liner.
