If you are breeding for profit, you can use a 10 gal tank, but you need a pretty good filter to handle the heavy feeding. Most people who use 10 gal tanks for breeding have several tanks hooked up to a central filtering system.
When I was breeding, I used 20 gal. tanks and set them up like little reefs with sumps and skimmers. I also used anemones (which very few people do), which meant good lighting. I found that my clowns bred more consistently and sooner, if they had an anemone.
Sometimes I was able to get clowns to lay on tiles, most of the time I just collected the fry with a flashlight and a scoop. In my case I was able to collect 100-200 fry with a scoop, which was plenty when it got time to sell. If you start collecting every batch of eggs (~every 10 days), it gets overwhelming pretty quickly even if you are just scooping. If you are good at raising the babies, you will have thousands of to sell in 6 month which is usually way more than you can sell in your local area. I also felt that I was getting only the strongest babies when I used the flashlight/scoop method of collection.