Does the water need heating?

If the sun bright enough, run the pump,
but check the ball valve is in the right position first, & change it if necessary.

But hang off a while if it's a frosty morning, (we don't want to cool things).

Keep going while temperature gain is Ok,
but ignore the differential if the water hasn't been circulation for 10 minutes to remove initial heat from the panels.

Decide if we need to switch to the heat pump if it's a lousy day.
If so, change the water valve position & try & use it at the best part of the day.

Make sure the heat pump is used in the evening to maintain required temperature,
Add a few 0.1°C's to the set temp if it's a chilly night to compensate for losses when the cover comes off.

When cycling the heat pump on & off, give it time to depressurise,
so it doesn't rotor lock,
and don't do something dopey, like just run it for 10 seconds.

Watch out for anything going wrong, like loss of water flow & icing evaporator.

Maybe give the main pump a whirl occasionally to stir up the mix.
Not good, toasty water at the top & chilly around the feet.