What warms more: open pool or covered with a black tarp?

[bjaspan]

I have a 12' x 30" Easy Set pool. I keep it covered almost all the time the kids aren't in it with a black, opaque tarp that is held down snuggly with bungee cords and covers both the top and most of the sides of the pool. My question is: On a hot, sunny day when the water is cold due to previous weather, is the pool likely to gain more heat while open or while covered by this tarp?

I know there are other active and passive heating solutions. I'm just asking if anyone knows the heating difference between open and covered.

Thanks!

 

[mknauss]

When the air is warm and the sun shining on the pool, that will warm the water much more than if it is covered at that time. Then cover once the sun is no longer shining on the pool.

 

[cj133]

I bet the ultimate would be a black pool liner uncovered during the day and using a good cover at night.

 

[Pv2]

black tarp will heat more than open, but you may be "cooking" the plastic parts directly under the tarp. on the other hand the sunlight damages them too so it may be a wash.