I've tried every regular brand of epoxy putty including the D-D product that is coraline colored and clouds the water with talc. I recently found the putty that is clearly the best for my use. It's a coraline colored Two Little Fishes product that comes in the same tube that the green product sold under several names comes in. None of these puttys including the Two Little Fishes product stick very well to frag discs or corals prior to curing. You can dry the bottom of your frag plugs or discs and still, the putty has very little adhesion. This makes it nearly impossible to glue things upside down! . So...........my method is this. Prepare my coloneys or frags that I plan to affix in position. Have them easy to reach with tools ready that I may need in a pinch. Towels, bone cutters, tweezers etc. I do NOT mix my epoxy prior to having everything ready. The Two Little Fishes product hardens very quickly (a plus in my book) so working time is less than 3 minutes. The good news is that as it begins to heat and set up, it becomes a "little" more stickable. I dry the bottom of the disc or plug then wet my fingers to prevent the epoxy lump from sticking better to me than the plug. I press and press and press trying to be sure to get good contact with the disc and eliminate air pockets. I also try to bring a lip around the edge of the disc to "cup it". I then quckly move the disc and epoxy formed to the bottom to the place it is going. With one careful and dedicated movement, I apply pressure to the top edges of the disc and watch for some displacement of putty. At that time I carefully remove my fingers so as NOT to disrupt the delicate bond. Within 15 minutes the epoxy is hard and "usually" holds in place. I always come back within a few minutes because sucess rate is still only about 60% on the first attempt especially if it's on a sloped surface like most are. It's a little science and a little sculpture art. I love it and I love my tank. Strong words.