When you're new to the hobby, as you are, It's easy to get sucked into all the hype regarding this and that filter media. Your stock will put out 'x' amount of bio load and your BB will multiply to a level which can deal with that load, no more no less. Put more fish in, bio load increases, BB numbers, in time, will increase to deal with the new 'x' number. This is a very basic dynamic of our hobby, yet possibly the most important part. The best thing is, the BB aren't fussy about what they grow on, they'll grow on any surface, not just in your filter either.
How do you know if your bio media is doing its job? How do you know if you have the correct type of bio media, or the correct amount? How do you know if your BB colonies are sufficient to deal with your stocking level? Easy.
Test your water.
