I don't mean to repeat what may have already been written, but I'll try to be brief.

I tried this last year and here is what I found (I'm located in Kentucky where the temps are moderate).

The fish are utterly worthless. They probably only reduce evaporation by 20-30% (I'm being generous I think). Additionally, to get any significant effect, you MUST turn your pump/filter OFF at night when the temps are the lowest to get the maximum benefit.

Additionally, the first fish I used last year, failed when the fish was 1/2 empty, leaving 1/2 of the 'liquid solar blanket' still in the fish (I used the 'Turbo' model with the 'computer controlled' pump).

The company replaced the defective fish (I was very surprised) but of course it is still very ineffective.

With experience with both the liquid blanket, and a standard bubble cover - I'd have to say that the bubble cover is well worth the effort (just ordered a new one).

If you are frustrated with your bubble cover style solar blanket and don't have a solar cover reel - spring for the $150 or so for an inexpensive model. It only takes me about 30 seconds to remove my 18x40 blanket, and about 2 minutes to put it on (by myself). Very little time, and very effective heat retention.