I have an older Euro Reef Skimmer that works great, however the pump has problems when starting after being turned off. It runs and pulls water but it is as if it struggles to pull air in. I can get it going by putting my finger over the end that pulls in water, which then causes air to pull and operate normally. The pump is a sedra 3500 and is about 4 months old. I have removed it, taken apart to ensure impeller is still good and all checks out.