Check your impeller in the Prizm, you probably have a 12 blade. They switched to an 18 blade impeller which made the unit quieter and also increased performance. Contact Red Sea and ask them to send you an 18 blade impeller. The Prizm (18 blade) does a good job, but I'd say that 55 gal. would be the max tank size I'd use one on. DIY skimmers are not difficult, and can be made with white PVC instead of acrylic. As long as you understand what makes them work (and what doesn't) you can build a good one, but you will need a sump first, unless you want the skimmer to be about 4 feet tall or so, the top would have to be 4-6 inches taller than your water level in the tank.