I have been using 10 gallon tanks to spawn in. I only put 3 or 4 gallons in and put a hood on to keep the heat and humidity in. what I like about the ten gallon is that there is plenty of room for the female to get away from the male. before they spawn they each take their sides and pretty much leave each other alone (except for a little playful harassment by the male). then when they are ready, they come together and spawn. when they are done, she usually returns to her side while he tends the nest until I get home to get her out. I haven't had any females get injured in a ten gallon yet. not that it wouldn't happen, but so far so good. I also crank the heat up to at least 82 degrees f.