Those cartridges are okay for fresh, but get used up fast in salt. They will help, but will need to be replaced often (maybe more than 1 a week).
What you could do in the mean time is go to the store and get a package of knee high nylons. Go to the petstore and get activated carbon. Probably going to be Black Diamond or similar in a half gallon container (just a bunch of black particles). Put this in one of the nylons, tie the nylon. Rinse under tap water for 20 seconds (get the dust off). Place in the hob if it is still there. Place on a overflow part if that exists. Just not sure what you have done yet.
I have done this many times in smaller or qt setups. Works fine. Then, in a couple weeks, change it out.