Kamil,

No its not algae, its fungus. Autozen informed me that it is a fungus not algae. I did some research and found that he is correct. So we should start calling it by the correct name: Fungus.

A biocide is the only additive that will kill the fungus. Biobor is a brand name of a biocide you can use. Diesel Doctor is no longer available and was made from Biobor. Biobor is not approved for on road use by the EPA so its hard to find but you can find it at some marinas. You also can find where it is available by doing an online search.

If you don't kill the fungus and just clean it out of your tank and replace the filters, It will eventually reappear.

P E H