Heating system flushing advice please

[stonedagain]

Whilst replacing a radiator recently, I noticed that the water is black & horrible. I have a couple more to replace shortly. I would like to flush my heating system before adding an inhibitor. Which are the best products to use, Fernox or Sentinel?
Thanks in advance.

 

[oldplumber]

you pay your money and make your choice, all much of a muchness, I like Primary care 3 sludge remover (£4.50 plus vat) from my merchant and my boiler rep from remeha was happy with that choice as its all the same in the end.