I've had an 8 Gallon Biocube for about 4 months now. I have one snail, one hermit and two ocellaris clown fish. About a month or so ago my tank started getting absolutely dominated by green and red diatoms/cyano bacteria. I've dosed the tank with chemiclean 5 times following the directions to the tee(wait 48 hours then 25% water change) with absolutely no results. I can't seem to get rid of this bacteria and it makes my tank look like a cess pool. Also, the rate the bacteria comes back(significantly) after cleaning is around only 2 days. Very frustrated, please help.

Additional info on the tank: 1.025 salinity, Temperature around 72 degrees(I know thats a little low), stock filter pads with carbon still inside, second chamber contains bio balls, Tank light on timer for 6 hours of daylight and deep sandbed.

wondering can you keep the tank away from natual sun light?
Is this stuff just on the glass? as I sometimes ge a little bit of a white kind and use a filter pad to wipe the inside of glass then the fish just feast on it all, and it seems to cure it that way. However im only guessing as not had your prombem before.

list of stuff to help you:
Get rid of the bioballs or clean them every few weeks, add live rock if you dont have any.

do more water changes, diatoms/cyano love nitrates and phosphates so getting rid of this, gets rid of their food source.

Make sure you dont have anything lower than a 6500K lighting source, the lower red spectra are preferred by the diatoms/cyano.

Add some macro-algae to the filter to help scrub the nitrates and phosphates out continuously.

Clean the filter pads every other day or get rid of them completely. these get a lot of material on them and raise the nitrates and phosphates significatly.

get more hermits and snails as well as some types of shrimp that eat the cyano..

Make sure you have enough water flow so they dont have a chance to stick to stuff as much.

Make sure your lighting periods are 12hrs or less.