Quote Originally Posted by mermaidwannabe

You say the tank has it's own built-in filter. Usually, one needs a filter rated at least twice the volume or gallonage of the tank. You might consider adding an extra (external) filter, and seed it with established media so it grows the BB colony faster.

The danio that is swimming erratically may have a swim bladder issue.
I agree with the filter issue. Many tanks come with a filter that is indequate for a stocked tank - therefore, a 10gal tank comes with one rated for up to 10gal which isn't enough for a 10gal with fish in it.

I also agree that the bacterial bloom would indicate you lost some of your BB along the way somehow.

I would also do larger than 25% water changes at this point (more like 50%) - even if they don't help the fish you mentioned, you want to avoid further stress/illness until you can start testing your own parameters.