Your in luck. Do some googling on a Reef Octopus 800s. This is the next best thing to ATB Hang on Cone Skimmer which costs over $1000 and the Deltec Hang on back which cost $600. It works great and pulls alot of scum out of the water. I recently took down my saltwater tank which was a 90 gallon. It's only 5 months old and ready to go. If you want it PM me. I'll give you a good price
The best is:
1. ATB Hang on back cone skimmer $1000
2. Deltec Hang on back skimmer $600
3. Reef Ocotopus 800s $240
4. Warner H2 hang on back skimmer $300
5. AQUAc REMORA
CPR BAK PAK 2
This is my order of best hang on back skimmers. #1 being the best #5 being the worst. This is just my opinion. Their also other hang on back skimmers but these seem to be the best.