I use the seaclone on my 55 as well and am very pleased with it.
If you are looking on ---- though I would caution about getting a seaclone as the odds are it will be an older model seaclone and will require modifications to make it work properly.
If there is a picture of the seaclone skimmer look at the center riser tube, if it is only a few inches long it is a newer model and will work great, if the center riser tube extends to the top of the skimmer it is an older model and it would be best to not purchase it.
Good Luck !!!