| Welcome! Too many lurkers never speak up. And that's a good question. I am not certain what all Waddy may have had in mind. I've learned that he often provides his bottom line advice without laying out all the reasons. I would expect his concern relates to maintaining high oxygen levels in the water being filtered, maximizing the nitrification process while minimizing the risk of potentially harmful heterotrophs being given a large homeland within the filter. If that is all that is behind the recommendation, then I'd say it is a rule of thumb that can be varied if the particular system is able to maintain adequate oxygen levels. Much will depend on flow rates, temperatures, etc. However, I am not sure if that is what he had in mind, or if there is more to it than that. |