I'm having a serious senior moment today. I just rinsed out the tank filter and realized I have NO clue why there's carbon in there. Since there's none in a pond filter, what's so special in an aquarium? :ph43r:

Carbon absorbs all sorts of things. It's not specific for one thing or another but seems to prefer organics. In an aquarium, it's normally a lot more crowded than a pond. Plus, we'd like our tanks to be crystal clear. The carbon removes the organics and improves clarity. There's no reason that you can't have carbon in a pond filter. My PondMaster has a tiny bit of carbon. I put some Ammo-carb in a mesh bag in my 1800 gallon pond filter. The thing is that the box I put in is way too little in my huge pond to make much difference. I don't bother to change it out or put in enough to really remove as much as the carbon in my tanks do. It would just cost way too much. The large containers of carbon I get cost $17. It's fine for your tanks or ponds to have carbon in the filter but it's not required to keep the tank or pond functioning. Some people don't like carbon for their aquariums because, at least in the case of planted tanks, it can also remove the micronutrients that plants need.