Flow Rate help: first tank

[sphelps]

The 3/4"bulkhead won't make a difference. The head loss resulting from smaller pipe is from friction alone so that 50gph loss you're seeing is purely from the extra friction from the length of all the pipe and fittings. Increasing the pipe and fittings to 1"will still give you the same gain despite the bulkhead at the end staying at 3/4", this will only act as a nozzle increasing velocity but flow rate for the most part will be unaffected. I should add I agree the pump is a bit small, personally I like to run larger return flow rates to cut back on the need for supplemental from powerheads.