It works for nanos. I have a 2.5 gallon with that potting soil capped with sand, and it is doing pretty well. One thing I can say is that whether it's 1 gallon or 100 gallons, rescaping is messy and I would advise against it unless you have a lot of time for clean up. Even in my 2.5, if I'm moving a well rooted plant, it takes the soil up through the cap and makes a mess. The method works, though. I like it because you don't have to worry about strong light, ferts or CO2, and the plants will still grow pretty well.