I have a green spotted puffer thats about 2 inches long currently. I wouldn't suggest putting him in a tank with pretty fish, mine ate one of my african cichlids so im sure he could take down an angel, or at least rough him up quite a bit. Have you tried taking the plants out and rinsing them off as well as possible, its just one more step that could help your problem. Its may take some time but if you can rinse off the egg sacks you can at least stunt the population growth. I cant seem to breed enough snails at times to keep my fish happy, of course i dont use them as the primary food, more like a treat. If your not soft hearted or weak stomached you can just crush them with your hands inside the tank, its faster then picking them out. The shells will eventulaly break down. And in a tank that large it shouldnt push your biological filter over the edge.