I needed at least ten gallons for an ATO Reservoir that wasn't higher than my sump (so that it wouldn't self-siphon), so here's what I can up with.....the water cooler concept reservoir....using a five gallon bucket from my pool, and a water jug. Simply cut a circle out of the top of the lid. The siphon point is the level of water in the bucket, not in the jug, and the bucket level was below my sump level. The water jugs also make changes very simple.
I did have to re-enforce the top of the lid of the bucket, so a donut was made from 1/2 acrylic.
A simple paneled cabinet was made to cover the reservoir.
This actually was a three sided cabinet on four casters that is easily pulled in and out.
And finally, to know when it needs a new jug of water, a horizontal float switch was installed in the side of the bucket.
This float switch simply lit an LED that was in the face of my equipment cabinet.