I have reared many freshwater angelfish using this method....Im not sure if it will work for clown fish, but I will jump on the soap box for a sec.......
The layed their eggs on a leaf a couple times, it was there spot....so I put a peice of slate rock in front of the leaf...the next week they laid eggs on the rock instead of the leaf....I then put the rock with an airstone in a small tank. The babies hatched in there, and you could feed them baby brine easily.
After that grow a little they are hardy as fug.
And I know, I know.....fresh water is for top offs and drinking, not aquariums.....salt is for fishing and fish tanks