I think it is helping me keep my ammonia levels down. But I had a faulty test before were as I have a proper water test it's ok. But I'm still going to use it just incase I end up with another ammonia spike.
Have used this product for almost three years in an external filter. It works perfectly when water checked at regular water changes, no ammonia imbalances found. Fish longer life found.
Have used this product in a Fluval 206 external filter for almost 5 years. Never had a problem in the tank but do replace on a regular basis. Excellent product.