Hi,
Mine is in sump model but I do have a upgrade kit that can turn this skimmer into an external one. You will just need to drill some holes on the reaction chamber tho.
I forgot to mention that I will also include an extra Euro Reef SP3 needle wheel pump. You can keep it as a spare. Or you can increase the performace of the skimmer by drilling an extra hole for the pump.
Please let me know if you have any other question.
