No doubt a DSB has it's pitfalls and although I know I will have to eventually replace mine it's worth it IMHO because of it's NNR ability. If you have a large tank a DSB may not be a good option because of the amount of work involved in replacing it so a BB or a SSB may be a better choice. I find it amusing how many who opted for BB tanks eventually went back to a DSB because of nitrate problems
