varable speed pump

I'm looking for suggestions/options on an equivalent replacement for our Single Speed SuperFlo 1HP with a VS pump (ran pump 16hrs/day last year to keep pool heated and clear, electricy was crazy, so was the sound) Our pool is 10k, 1 return & skimmer, pump is located ~1ft higher than water...

I have a new pool build. 21,000 gal. 2.75 HP Hayward variable speed pump with Hayward 4 cartridge filter and salt generator. Not long after my pump switches from 85% to 50%, a small bubble forms at the top of the reservoir. The longer it stays at 50% the bubble becomes larger and larger until...