20 gallon long? or 20 gallon high? The 20g high should be fine. As far as the 20g. long, I would be a bit cautious. If the support is mainly around the edges, it's unlikely that you would be able to keep a 10 gallon there without some kind of bowing of the top of the stand.
Yeah sure, and actually you probably can have a 20 gallon tank on a stand designed for 10 gallons as it will be able to tolerate the weight, unlike someone said. I have a 100 liter tank on a 65 liter stand and it's been like that for a long time no with no problems at all!
