Okay. Took me a while to find the filter, take the photos, upload them, etc. I'm old. Gimme a break.
To remove the carbon from your filter:
1. Separate the cartridge from the top part. Just hold each end and pull apart.
2. Then, pull the bottom out of the cartridge to remove the sponge and carbon.
3. You'll see where the little carbon basket is held on by the strips of black plastic. Just pop the strips out of the little groves on the basket and viola! You've removed the carbon.
As far as how I cleaned mine, I would just follow the above steps to remove the sponge and gently squeeze it out in the old tank water I had removed during the water change. I would squeeze it once or twice and brush off any gunk and then put it all back together.
I can't remember now how often I would replace the whole cartridge, but when it begins to look old and worn out, you can buy replacement cartridges at Petsmart.
I'm not sure if just leaving the carbon in all the time is harmful or not. I've just always removed mine due to having live plants and not wanting the carbon to absorb any of the nutrients they need. I only use carbon after medicating or to remove tannins.
I'm glad Crusoe is feeling back to his old self again!