Hmmm...a couple of ideas. First, you don't necessarily need a sump for a saltwater system..you can use the AQ 110 but you want to make sure yo have good flow thrioughout the tank. Given that this is a "tall" tank, the flow from the filter may not be enough to get to the bottom. You can supplement the flow with a powerhead on the other end; maybe position it a little further down in the tank. I had a 75 gallon. I used the AQ 110 Filter at one end and a sponge filter at the other with an AQ 110 powerhead; I had no circulation issues.
Second, is your AQ filter in use now in a FW
or is it new? If it is in use or has been used, you might want to get a new sponge. The bacteria that thrives in a FW
system won't live in SW
. You can either get a new sponge, or, boil the sponge you have to make sure all the bacteria, dirt, embedded food etc is cleaned out. You want to start your SW
out with as clean equipment as you can manage.
If you want to look into what it takes to construct a sump, just do a search for constructing a sump. I know I have seen articles out there.