I currently have two aqua clear HOB
filters they both are large one bigger than the other a 50 and a 70 i think. I use sponges and charcoal in them but its not working with this tank they don't seem to do the job.
I have another tank a 55 galon cichlid tank with an aqua clear 50 on it pretty much the same set up sponges and charcoal only in this tank it does great water stays clear and the filter is always an ease to clean not too much grime built up in it i can simply rinse everything off good and put it back in and everything works great.
With my bigger tank the 100 galon i really need to give everything a really good clean everytime because the grime really builds up in my filters its a real pain and unlike my other tank i can't reuse my charcoal or sponges everytime because they get too nasty. The filter in my 55 has a small pack of ammonia rock but i don't think this has anything to do with why it works on my 55 and not my 100 because the ammonia rock pack is old i doubt they are anything other than just rocks at this point. I guess it wouldn't hurt to try ammonia rock in my 100 gal