I'm so glad to see this thread, since I'm already planning Lucky's upgrade and I want to divide a 10 gallon tank so I can have a second betta. Is there anything I need to know about picking up aquarium sealant? When I read how to make your own dividers, they mentioned using that to glue them in place. I'm looking at Marineland Silicone aquarium sealant.
I also like the double divider idea, since I won't have to worry so much about whether or not the current is too strong when I get a filter for a 10 gallon tank. For a sponge filter, is the 10 gallon setup going to be enough? It's the Elite single sponge filter with the Tetra 10 gallon air pump.