Regulations regarding the need of a lifeguard in a pool are regional. If your development is in Andalucia:
LIFEGUARDS for ANDALUCIA POOLS
Every collective use pool with a water surface greater than 200m2 must have lifeguard services. The lifeguards must have the official certificate for life guarding. The number of lifeguards will be required as follows:
A) One lifeguard for pools from 200 to 500 m2 of water surface.
b) Two lifeguards for pools from 500 to 1000 m2 of water surface.
c) For pools bigger than 1000 m2 of water surface, one lifeguard will be added for every vessel or 500 m2 of water surface
Regardless what is stated above, if the separation between pools does not allow an efficient watchfulness, a lifeguard will be required for each pool as a minimum.