I've got an idea... how about a plating frogspawn!
Frogspawn are great and available in a lot of different varieties. I rarely see the plating variety, and the one in my tank is so large now I could split it four ways if I had the right tile saw ad WAY more courage than I do.
Also consider hammer... or both...
The plating variety of either produces an animay your clowns can really get themselves deep into, the branching, under good conditions, will provide you with enough frags to last a lifetime. Whichever you add, however, make sure to religioulsly dose calcium and alkalinity.