Usually you get better responses to your questions here on AA then this one.I too have been running canister filters for years and have had Cystall clear water and have just recently switched to a sump system. Was blown away with all the confusion about sumps. But once you figure them out, get them running right, they are pretty sweet!
I believe what your wondering about is that you are not happy with your 20 gallon "Sump" that you acquired and want to go with a larger sump. The sump pump is part of your sump system and you don't make them, but buy them. jvision answer was a recommendation on a pump you could buy for your sump. The pump you select can be of many variations ac powered vs dc powered, with different flow rates specified that needs to be selected on size of tank you have. The height the pump (head) has to pump the water up to, and about how much flow you want. A 2000 gph flow pump may only pump 1000 gph at a head of 5 feet. How much flow you need is determined by many factors but to start with you might look at 5 to 10 times your tank volume, so a 1000 gph pump would work on a 110 gallon tank. I have read where some guys run as low as 3 tank volumes with few fish, some like it really high ( the reefers ) high bioloads 10 times + the tank volume. If you were going to go with ckmullin suggestion and have only plants it would be child's play to figure how how little flow you would need.
Now as far as your other side of your question about a different sump. ...not sump pump...you can purchase one from Big Al's online. They are pricey but very nice ...I had just purchased one of there Trigger sump systems. I see they have a 20 gallon trigger sump which would probabably work well for your 110 but at ~ $400 you might want to build one if you are handy. I bought the Cystall elite 36 which gives you about 35 gallons of sump volume running it on a 150 gallon. More money You could probably have one of the tank builders put one together for you cheaper if you figure you are not quit capable. But you might have to spec it out for them even though they could probably build one with you saying you wanted 30 gallons of volume. You will still need to do much more homework before making a decision for which ever way you go.
Further on Sump Pumps which are normally submersible .... on my sump I run two pumps backing each other up....both pumps having a reputation to be being very quiet, (mag drive pumps have been known to be a little noisy and like to consume electricity ) a power hungry ac powered Eheim and a dc powered Tunzi which consumes about half the power of my ac pump, quieter, smaller, and has a variable flow rate, unfortunately is more money to buy again. Lots of research and what sucks is most of the info on the web for sump systems and pumps for those systems is with regards to saltwater. Google BRS videos ...Bulk Reef Supply.com ...they have many videos about setting up sumps, sump systems, and overflows, and some videos on sump pumps designs, however keep in mind again these are videos for salt tanks. But because it salt don't totally disregard it as some of these reefers are pretty sharp fellows!
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