WOW! $250 for Levis!!!! Where on earth do you live...the US!!!
You should be able to keep 3 happily in a tank that size. Unfortunately they are INCREDIBLY hard to sex, even as adults. Thankfully mine are a breeding trio, so obviously I know what sex they are. I will try and take some pics of the undersides of mine for comparison.
I MAY have a spare pair of them, but it will depend on if the last three eggs are successful. Fingers crossed LOL!!
Have just taken some pics of them for someone else, so will upload them to photobucket and post them here...
:0)