uh.... a falco hawk and a clown in a 10g? I think all hawks with the exception of geometrics need at least 20gallon or a 10gallon by them self. They also rip any crabs/shrimp to shreds.
Have you researched the cucumbers? they are ticking time bombs. Even more so in smaller tanks.
Here's a good read: http/www.wetwebmedia.com/seacukes.htm