May I guess that what's afoot is this:
Our new 120 gal vertical above ground tank seemed perfect to fuel the smallest fireplace gas logs over a season BUT (at least this first year) it is addictive - as would swimming in a heated pool in cooler months will be.
Soooo we have had at least 3 refills this season thus far! (since I don't have to cart heavy tanks to refill points.)
Thinking a pool heater will eat more fuel, certainly if swimming in cooler months might be = too many refueling stops for the supplier, which could translate to your costs rising.
Agree the pool heating guys have no problems, IF the supplies don't run out.
I won't debate the underground vs above here, only to say that above ground easier to inspect = safer and fencing/evergreens are screening elements found every where be they for aesthesis or propane tanks.
Fun fact: propane is not perishable but pricing depends on demand/supply/weather/politics sooooo bigger tanks is better when serving a dedicated appliance .... HVAC, WH, generators, then perhaps swimming, fireplaces, BBQ, etc.
Ten words or less ... a goal unattainable