carbon?

what kind of carbon should i use in my hob filter?

 

Granular activated carbon.

 

what brand and do i need a sock?

 

Bulk Reef Supply ROX 0.8 is very good, as is seachem matrix. I am currently using black diamond, it is lower cost, but very effective. The downside is BD has more dust and some people are concerned about this due to a possible, but yet to be shown association between dust and Head and Latteral Line Disease in certain fish, such as tangs. To be safe, I would recommend rinsing it very well though if you go that route.

As to the sock, pour it in a bag, and put it in the filter, not a sock. The cartridges are expensive and you are stuck with their brand.

 

What kind of HOB do you have? Most of the HOB's you can buy cartridges for, which already have carbon incased in filter floss, and are made to fit your filter and you just drop it in.

Another option is to get a media back or (sock) and fill it with GAC and drop it in your HOB. I would recommend BRS - Bulk Aquarium Supplies - Reef Aquarium Supplies | BulkReefSupply.com for getting that stuff. They have a video on their site explain the different types of carbon that they carry.

 

ive heard that the ones i can buy for the filter somtime leach bad stuff into saltwater

 

I believe all carbon catch leach whatever it has absorbed if you leave it in too long. It should be changed at least monthly and more frequently is better. I try to change mine every 2/3 weeks.