Sump on a nano ?

[Acipenser]

I am having a Heck of a time trying to get the flow balanced out from my 15G to the sump and back. My thoughts are that the tolerances are just too small . I have 2 - 1/2" drains and a Eheim 1000 pump with 1/2" return from my 5 gallon sump. on the drains I have 2 ball valves so I can adjust the flow. I cant seam to find the proper balance and am questioning weather I should just not plan for a sump on such a small tank - Thoughts ?