200mmD tank, 800mmH and about 1.2mL going in a wall but it has to be solar powered at 12v. He's got a 20w solar panel already setup to run anything for the tank with a heap of batteries in line.

He's only going to run cold water fish so heating's not a problem but he's asked me to think about filtration as everything he's come across internally is 240v.

My initial thougts were a sump beneath the tank but it's not possible unless the sump is at least 2m under the tank and that creates a flow problem with DC pumps and the amount of wattage he has to play with.

He's also away from the property for 2 weeks at a time.

My thoughts......

A 1000lph 12v pump and a small acrylic sump in the top of the tank about 20cm deep and 400-500mm long. Put a few sponges in there and then a couple of baffles with Bio Balls and Noodles etc. Pump pushes water from the tank in to the sump and simply gravity feeds back to the tank from the bottom of the sump, hopefully with a bit of a splash so it creates some surface movement too.

Anyone ever done this using solar?