Um ok WAter trough - money permitting... If not, cos they costa lotta!... I used the water storage tanks from Wicks. The large ones cost about £25 if my memory is correct. They are squarish and black. They lasted me a few seasons, even in the icey weather.
They just didn't stand up to a Friesian youngster climbing in them and using it as a splash pool.... *roll eyes*
A huge, black rubber trug - it's enormous. I think it's some agricultural or building thing. It looks like an ordinary big trug but it is about 50 litre capacity. It used to freeze solid, but never split.
75 litre tubs with heater units in winter, 75 litre plastic Home Depot (B&Q) tubs in the summer they cost $9 and are easy to move about.
Other paddocks have self filling/heated troughs.
We have a huge concrete trough. it was a complete find as we bought the field with no water supply. On further investigation we found the trough planted up as a 'pond', full of reeds and stones. Several hours later it was clean and with the added bonus of an intact water supply - finding it made my day
I use trugs. My ponies are strip grazed, 3 are in separate pens and 2 mares are in together. They do need filling probably every other day in summer but they are easy to move as I move the elec fence.