I had used carbon for years and never had a problem with it. But the OP is talking about using it for his filtration for water used for top offs and changes not running continuously in his tank filters. Big difference.
No difference at all if dust is in the water column for any form of use. Whats going to stop carbon dust from getting into the water column of the tank unless he's also using a micron filter before the water goes into the tank. Dosnt need to be a continuous source of filtration. Even slipping a cartridge into a HOB dust is released into the water column. Where ever carbon is used, it runs a risk.
I've been dealing with cichlids for 20 years, and i'll tell you i havnt used carbon in a couple years now, and there has been a definite change in not only the fish health but the biotopes of the tanks as well. I only learned of the risk after a well known fish supplier came to my house 2 years ago to buy my lot of geophagus sp. topajos redhead juvies off me, and noticed i had HITH on some fish in a few tanks i had running, and asked if i used carbon. He then explained to me how he dosnt nor are a lot of well known breeders using it anymore, and are convinced it's carbon being the culprit. Is it healthy for us as humans? Not as bad as asbestos, but not exactly healthy for us either lol
It's a on-going discussion in cichlid forums & other forums i'm apart of, but more, and more of us are ditching it, and getting on just fine if not better without it. I can link all sorts of studies, but i think it's best for people to read this, and do their own research. I'm a fish guy getting into plants recently. I have a lot to learn about plants which is why i came to this forum as it seems to be the best, but i also notice a lot of plant guys arnt well versed into the fish aspect. So hopefully while i learn from you guys on plants, i can add to the fish discussions on here
Am i a fish guru no, but this carbon debate to me is something serious to consider.