you can use hydrogen peroxide as mentioned above, but use it only if you have no other choice.
I'm confused by this advice. Using H2O2 is the least evasive treatment to the water column. HP burns the cell wall on the bacteria killing it and in the process breaks down becoming inert. Staying at a daily dose rate below 2ml/g is 99.9% safe by all reports from those that have used it. Fish and plants can remain in the tank safely during treatment. Daily vacuuming and spot treatment over a week's time has made this stuff disappear the few times I've seen it in the last few years. Used antibiotic treatments in the past and the cost is high for larger tanks along with the other draw backs to doing that.
UV sterilizer use at the correct dwell rate kills it once it's drawn through the unit. Having several of these it was used also when I eliminated BGA.
Opting to use antibiotic treatments with the known effects on the biological filter and possibility of repeating the tanks cycle why waste the money? Drastic treatment for those impatient for results could still be done cheaply with HP. 3% topical hydrogen peroxide is about a $1.00/Qt.
Clean the tank and filter then treat @ 10ml/g
Treatment of 10mL per gallon is the dose used to kill algae and practically all bacteria and parasites, protozoans, etc. Established treatment at this dosage is to isolate the filter (shut it down to save your cycle bacteria) allow for circulation with a power head or air stone. 3-5 hour stand time on the treatment then do a 50% water change followed by a 25% water change after 24 hours. The filter can be restarted after the 50% water change. Delicate plants can melt but what was in the tank, be it algae or bacteria is toast.
This is the highest dosing of HP recommended by fish breeders on my other favorite website. I've used this dosing level twice to good result on scaled fish and followed the water changing recommendation.
HP has strong oxidizing properties. It is a powerful bleaching agent. The oxidizing capacity of hydrogen peroxide is so strong that it is considered a highly reactive oxygen. (Wikipedia)
Pleco, Cory and loaches can react badly to high doses of HP. Remove your fish to a separate tank and expect a cycle at 10ml/g if the filter is left running. There are tons of HP threads on the web because it's cheap and it works.