Keep the DSB. It should be at least 4" and upto 6". Make sure you know the facts before you start making any major changes. There are many very qualified people who strongly support DSB's, including Shimek, Boremann, Frayley, Fenner, Calfo, just to name a few. Read any book or thread by these guys on the topic to get their opinions. Then, to to -- and you will find several long winded topic threads, some for DSB's some against. After that, decide for yourself what to do, but don't just take someone's single opinion that DSB's are good or bad.
IMO, for what it is worth, I have had a DSB for rougly 4 years. Mine does not look like your's, but it has in the past and it is normal. My Nitratres/ etc are all low (not zero but I don't skim, which is a topic for another time). I am a personal fan of the DSB and no one has ever given me any concrete evidence that the theory behind a DSB is flawed or that a PROPERLY maintained DSB will crash.
Just make sure you decide yourself, and if you go the DSB route, make sure you know how to maintain you DSB and tank. It is different than using system without a DSB.
BTW, you can use a credit card or razor and scrap that stuff off if you don't like the look of it. Just make sure not to disturbe the DSB much when you do.