I have read several threads but none that exactly answer my question. I recently picked-up a 90g Reef Ready tank and the original owner also threw in the skimmer. After getting everything home and cleanup I realized the the pump is no good. I was going to buy a replacement but have seen some posts recommending the sendra 5000 rather than the 3500. The pumps are $99 and $75 respectively. Any input would be greatly appreciated.