Balsa de agua is a water tank and filtration firm based in Benahavís, in Málaga province. Its Google Business Profile lists it as “Rainwater tank supplier”.
It has a Google rating of 2.0 from 1 review. That is too few reviews to say much yet, so ask for references.
Nearby alternatives for a second quote: Torre depósito de agua in Benahavís (5 km). Getting two or three quotes is normal for this kind of work.