I use a 40w panel to run a Oase Solar 700 pond pump, both are now around 10 years old. On full chat according to the makers figures it will shift 700L an hour using 8watts but that would be max 2m head . From about now to the September in conjunction with an 80 amp hour leisure battery it ran the water feature for quite a few hours a day and some pond lights till about 11pm till a time switch turned them off but there wasn?t much reserve if there were some cloudy or rainy days. Later I installed a relay coupled to one of those tiny battery charging panels so when the conditions allowed for some solar generation it closed the circuit from the pump to the battery .That stopped the pump flattening the battery, the solar charge controller would have switched it off eventually it I didn?t want it to go that low. From about October to May the charge controller took more power than was being generated so the system got mothballed for the winter. If I was doing it again I would definitely go for a larger panel as they are much cheaper relatively than when I purchased mine. As it I have since got mains to that area of the garden and the battery failed a while back so I have removed the charge controller and battery and the panel is now connected directly to pump. Sun comes out , Water feature runs.
There are quite a few solar pond pumps systems advertised , the Oase pump one was quite expensive 10 years ago and many of the complete systems advertised now are a lot cheaper. I suspect I could pee more than most of them. For reliability and to work it will not be cheap.
GH