This protein skimmer is a seaclone 100 made by instantocean.
It can be run either as a hang-on or in-sump. I have used it both ways. Rated for 100 gallon tank. Was on my 90 gallon with no issues.
I did have it running in my sump so it does look used. Still works great. Was just using it but it is too big and overkill for my nano.
I bought it from bigals.
http://www.bigalspets.ca/seaclone-pr...immer-100.html
Looking to get $70.