The down tube is 1.5 inch but it is not backing up at all. The problem is from the fist stage to where the water flows over the wall in the second stage to the down tube.
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72g Bowfront Drilled,Lighting,2x250 10,000k MH,2 actinic T5,2/6" fans,2MJ with 1600gph convertions kits,Bullet 2 style skimmer with Mak 4,29g sump/Refugium,96W power compacts in sump, Velocity T4 Titanium "return",Life Guard 300 Fluidize bed filter,1"sand bed, 29g auto top off, 140lb LR,SPS,LPS,Softies,Zoos,2Percula Clowns, 2yellow tail Damsels,1yellow tang,2cleaner shrimp, 1six line Wrass,2 Bengaii Cardinal,1lawnmower Blenny,1sand sifting star,1TigerTailCucumber, snails,hermit crabs,Macros.
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