Thanks for all the replies! With your comments and other research it looks like I can't run it without a pump, the venturi needs a good pump for good efficiency. I had my skimmer setup in Chicago for 1 year then took 4 years off from the hobby, I might have been running the skimmer with my Rio1700 before, but not sure.

I know the Rios are terrible(newbie mistake a long time ago), but I'm waiting for a cheap used pump to come along. Drilling a bulkhead is not an option as I have no room in the stand to have an external pump. I think I might try to get a 29 gallon tank which is taller and shorter length and make a brand new sump with a mag7 external pump. For now I think I'm going to just put more cheato in my frag section to increase the space for it.

Thanks again for the replies!

Brian