Metal racks for 3 foot tanks

Hi guys

I am thinking about making some room for more tanks.

I currently have 2 tanks that are 3ft x 14" x 20" sitting on individual stands. I am thinking about racking this guys, one on top of each other, with room down below possible for a sump or something ... haven't thought that far.

Anyone suggest an easy solution to bolt some metal together to create a rack. I don't have a workshop at home but can get equipment if required.

At one stage I was also considering those boltless racks you can get at Bunnings.

Thanks in advance ;)